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Covalent bond

A covalent bond is a chemical bond that involves the sharing of electrons to form electron pairs between atoms. These electron pairs are known as shared pairs or bonding pairs. The stable balance of attractive and repulsive forces between atoms, when they share electrons, is known as covalent bonding. For many molecules, the sharing of electrons allows each atom to attain the equivalent of a full valence shell, corresponding to a stable electronic configuration. In organic chemistry, covalent bonding is much more common than ionic bonding.

Covalent bonding also includes many kinds of interactions, including σ-bonding, π-bonding, metal-to-metal bonding, agostic interactions, bent bonds, three-center two-electron bonds and three-center four-electron bonds. The term covalent bond dates from 1939. The prefix co- means jointly, associated in action, partnered to a lesser degree,  etc.; thus a "co-valent bond", in essence, means that the atoms share "valence", such as is discussed in valence bond theory.

In the molecule, the hydrogen atoms share the two electrons via covalent bonding. Covalency is greatest between atoms of similar electronegativities. Thus, covalent bonding does not necessarily require that the two atoms be of the same elements, only that they be of comparable electronegativity. Covalent bonding that entails the sharing of electrons over more than two atoms is said to be delocalized.

History

The term covalence in regard to bonding was first used in 1919 by Irving Langmuir in a Journal of the American Chemical Society article entitled "The Arrangement of Electrons in Atoms and Molecules". Langmuir wrote that "we shall denote by the term covalence the number of pairs of electrons that a given atom shares with its neighbors."

The idea of covalent bonding can be traced several years before 1919 to Gilbert N. Lewis, who in 1916 described the sharing of electron pairs between atoms (and in 1926 he also coined the term "photon" for the smallest unit of radiant energy). He introduced the Lewis notation or electron dot notation or Lewis dot structure, in which valence electrons (those in the outer shell) are represented as dots around the atomic symbols. Pairs of electrons located between atoms represent covalent bonds. Multiple pairs represent multiple bonds, such as double bonds and triple bonds. An alternative form of representation, not shown here, has bond-forming electron pairs represented as solid lines.

Lewis proposed that an atom forms enough covalent bonds to form a full (or closed) outer electron shell. In the diagram of methane shown here, the carbon atom has a valence of four and is, therefore, surrounded by eight electrons (the octet rule), four from the carbon itself and four from the hydrogens bonded to it. Each hydrogen has a valence of one and is surrounded by two electrons (a duet rule) – its own one electron plus one from the carbon. The numbers of electrons correspond to full shells in the quantum theory of the atom; the outer shell of a carbon atom is the n = 2 shell, which can hold eight electrons, whereas the outer (and only) shell of a hydrogen atom is the n = 1 shell, which can hold only two.

While the idea of shared electron pairs provides an effective qualitative picture of covalent bonding, quantum mechanics is needed to understand the nature of these bonds and predict the structures and properties of simple molecules. Walter Heitler and Fritz London are credited with the first successful quantum mechanical explanation of a chemical bond (molecular hydrogen) in 1927. Their work was based on the valence bond model, which assumes that a chemical bond is formed when there is good overlap between the atomic orbitals of participating atoms.

Types of covalent bonds
Atomic orbitals (except for s orbitals) have specific directional properties leading to different types of covalent bonds. Sigma (σ) bonds are the strongest covalent bonds and are due to head-on overlapping of orbitals on two different atoms. A single bond is usually a σ bond. Pi (π) bonds are weaker and are due to lateral overlap between p (or d) orbitals. A double bond between two given atoms consists of one σ and one π bond, and a triple bond is one σ and two π bonds.

Covalent bonds are also affected by the electronegativity of the connected atoms which determines the chemical polarity of the bond. Two atoms with equal electronegativity will make nonpolar covalent bonds such as H–H. An unequal relationship creates a polar covalent bond such as with H−Cl. However polarity also requires geometric asymmetry, or else dipoles may cancel out, resulting in a non-polar molecule.

Covalent structures
There are several types of structures for covalent substances, including individual molecules, molecular structures, macromolecular structures and giant covalent structures. Individual molecules have strong bonds that hold the atoms together, but generally, there are negligible forces of attraction between molecules. Such covalent substances are usually gases, for example, HCl, SO2, CO2, and CH4. In molecular structures, there are weak forces of attraction. Such covalent substances are low-boiling-temperature liquids (such as ethanol), and low-melting-temperature solids (such as iodine and solid CO2). Macromolecular structures have large numbers of atoms linked by covalent bonds in chains, including synthetic polymers such as polyethylene and nylon, and biopolymers such as proteins and starch. Network covalent structures (or giant covalent structures) contain large numbers of atoms linked in sheets (such as graphite), or 3-dimensional structures (such as diamond and quartz). These substances have high melting and boiling points, are frequently brittle, and tend to have high electrical resistivity. Elements that have high electronegativity, and the ability to form three or four electron pair bonds, often form such large macromolecular structures.

One- and three-electron bonds
Bonds with one or three electrons can be found in radical species, which have an odd number of electrons. The simplest example of a 1-electron bond is found in the dihydrogen cation,. One-electron bonds often have about half the bond energy of a 2-electron bond, and are therefore called "half bonds". However, there are exceptions: in the case of dilithium, the bond is actually stronger for the 1-electron than for the 2-electron Li2. This exception can be explained in terms of hybridization and inner-shell effects.

The simplest example of three-electron bonding can be found in the helium dimer cation,. It is considered a "half bond" because it consists of only one shared electron (rather than two); in molecular orbital terms, the third electron is in an anti-bonding orbital which cancels out half of the bond formed by the other two electrons. Another example of a molecule containing a 3-electron bond, in addition to two 2-electron bonds, is nitric oxide, NO. The oxygen molecule, O2 can also be regarded as having two 3-electron bonds and one 2-electron bond, which accounts for its paramagnetism and its formal bond order of 2. Chlorine dioxide and its heavier analogues bromine dioxide and iodine dioxide also contain three-electron bonds.

Molecules with odd-electron bonds are usually highly reactive. These types of bond are only stable between atoms with similar electronegativities.

Resonance
There are situations whereby a single Lewis structure is insufficient to explain the electron configuration in a molecule and its resulting experimentally-determined properties, hence a superposition of structures is needed. The same two atoms in such molecules can be bonded differently in different Lewis structures (a single bond in one, a double bond in another, or even none at all), resulting in a non-integer bond order. The nitrate ion is one such example with three equivalent structures. The bond between the nitrogen and each oxygen is a double bond in one structure and a single bond in the other two, so that the average bond order for each N–O interaction is $2 + 1 + 1⁄3$ = $4⁄3$.

Aromaticity
In organic chemistry, when a molecule with a planar ring obeys Hückel's rule, where the number of π electrons fit the formula 4n + 2 (where n is an integer), it attains extra stability and symmetry. In benzene, the prototypical aromatic compound, there are 6 π bonding electrons (n = 1, 4n + 2 = 6). These occupy three delocalized π molecular orbitals (molecular orbital theory) or form conjugate π bonds in two resonance structures that linearly combine (valence bond theory), creating a regular hexagon exhibiting a greater stabilization than the hypothetical 1,3,5-cyclohexatriene.

In the case of heterocyclic aromatics and substituted benzenes, the electronegativity differences between different parts of the ring may dominate the chemical behavior of aromatic ring bonds, which otherwise are equivalent.

Hypervalence
Certain molecules such as xenon difluoride and sulfur hexafluoride have higher co-ordination numbers than would be possible due to strictly covalent bonding according to the octet rule. This is explained by the three-center four-electron bond ("3c–4e") model which interprets the molecular wavefunction in terms of non-bonding highest occupied molecular orbitals in molecular orbital theory and resonance of sigma bonds in valence bond theory.

Electron deficiency
In three-center two-electron bonds ("3c–2e") three atoms share two electrons in bonding. This type of bonding occurs in boron hydrides such as diborane (B2H6), which are often described as electron deficient because there are not enough valence electrons to form localized (2-centre 2-electron) bonds joining all the atoms. However the more modern description using 3c–2e bonds does provide enough bonding orbitals to connect all the atoms, so that the molecules can instead be classified as electron-precise.

Each such bond (2 per molecule in diborane) contains a pair of electrons which connect the boron atoms to each other in a banana shape, with a proton (the nucleus of a hydrogen atom) in the middle of the bond, sharing electrons with both boron atoms. In certain cluster compounds, so-called four-center two-electron bonds also have been postulated.

Quantum mechanical description
After the development of quantum mechanics, two basic theories were proposed to provide a quantum description of chemical bonding: valence bond (VB) theory and molecular orbital (MO) theory. A more recent quantum description is given in terms of atomic contributions to the electronic density of states.

Comparison of VB and MO theories
The two theories represent two ways to build up the electron configuration of the molecule. For valence bond theory, the atomic hybrid orbitals are filled with electrons first to produce a fully bonded valence configuration, followed by performing a linear combination of contributing structures (resonance) if there are several of them. In contrast, for molecular orbital theory a linear combination of atomic orbitals is performed first, followed by filling of the resulting molecular orbitals with electrons.

The two approaches are regarded as complementary, and each provides its own insights into the problem of chemical bonding. As valence bond theory builds the molecular wavefunction out of localized bonds, it is more suited for the calculation of bond energies and the understanding of reaction mechanisms. As molecular orbital theory builds the molecular wavefunction out of delocalized orbitals, it is more suited for the calculation of ionization energies and the understanding of spectral absorption bands.

At the qualitative level, both theories contain incorrect predictions. Simple (Heitler–London) valence bond theory correctly predicts the dissociation of homonuclear diatomic molecules into separate atoms, while simple (Hartree–Fock) molecular orbital theory incorrectly predicts dissociation into a mixture of atoms and ions. On the other hand, simple molecular orbital theory correctly predicts Hückel's rule of aromaticity, while simple valence bond theory incorrectly predicts that cyclobutadiene has larger resonance energy than benzene.

Although the wavefunctions generated by both theories at the qualitative level do not agree and do not match the stabilization energy by experiment, they can be corrected by configuration interaction. This is done by combining the valence bond covalent function with the functions describing all possible ionic structures or by combining the molecular orbital ground state function with the functions describing all possible excited states using unoccupied orbitals. It can then be seen that the simple molecular orbital approach overestimates the weight of the ionic structures while the simple valence bond approach neglects them. This can also be described as saying that the simple molecular orbital approach neglects electron correlation while the simple valence bond approach overestimates it.

Modern calculations in quantum chemistry usually start from (but ultimately go far beyond) a molecular orbital rather than a valence bond approach, not because of any intrinsic superiority in the former but rather because the MO approach is more readily adapted to numerical computations. Molecular orbitals are orthogonal, which significantly increases the feasibility and speed of computer calculations compared to nonorthogonal valence bond orbitals.

Covalency from atomic contribution to the electronic density of states
In COOP, COHP and BCOOP, evaluation of bond covalency is dependent on the basis set. To overcome this issue, an alternative formulation of the bond covalency can be provided in this way.

The center mass $cm(n,l,m_l,m_s)$ of an atomic orbital $$| n,l,m_l,m_s \rangle ,$$ with quantum numbers $n,$ $l,$ $m_l,$ $m_s,$ for atom A is defined as

 * $$cm^\mathrm{A}(n,l,m_l,m_s)=\frac{\int\limits_{E_0}\limits^{E_1} E g_{|n,l,m_l,m_s\rangle}^\mathrm{A}(E) dE}{\int\limits_{E_0}\limits^{E_1} g_{|n,l,m_l,m_s\rangle}^\mathrm{A} (E)dE}$$

where $$g_{|n,l,m_l,m_s\rangle}^\mathrm{A}(E)$$ is the contribution of the atomic orbital $$|n,l,m_l,m_s \rangle$$ of the atom A to the total electronic density of states $g(E)$ of the solid

 * $$g(E)=\sum_\mathrm{A}\sum_{n, l}\sum_{m_l, m_s}{g_{|n,l,m_l,m_s\rangle}^\mathrm{A}(E)}$$

where the outer sum runs over all atoms A of the unit cell. The energy window $[E_0, E_1]$ is chosen in such a way that it encompasses all of the relevant bands participating in the bond. If the range to select is unclear, it can be identified in practice by examining the molecular orbitals that describe the electron density along with the considered bond.

The relative position $C_{n_\mathrm{A}l_\mathrm{A},n_\mathrm{B}l_\mathrm{B} }$ of the center mass of $$| n_\mathrm{A},l_\mathrm{A}\rangle$$ levels of atom A with respect to the center mass of $$| n_\mathrm{B},l_\mathrm{B}\rangle$$ levels of atom B is given as

 * $$C_{n_\mathrm{A}l_\mathrm{A},n_\mathrm{B}l_\mathrm{B}}=-\left|cm^\mathrm{A}(n_\mathrm{A},l_\mathrm{A})-cm^\mathrm{B}(n_\mathrm{B},l_\mathrm{B})\right|$$

where the contributions of the magnetic and spin quantum numbers are summed. According to this definition, the relative position of the A levels with respect to the B levels is

 * $$C_\mathrm{A,B}=-\left|cm^\mathrm{A}-cm^\mathrm{B}\right|$$

where, for simplicity, we may omit the dependence from the principal quantum number $n$ in the notation referring to $C_{n_\mathrm{A}l_\mathrm{A},n_\mathrm{B}l_\mathrm{B} }.$

In this formalism, the greater the value of $C_\mathrm{A,B},$ the higher the overlap of the selected atomic bands, and thus the electron density described by those orbitals gives a more covalent A\sB bond. The quantity $C_\mathrm{A,B}$ is denoted as the covalency of the A\sB bond, which is specified in the same units of the energy $E$.

Analogous effect in nuclear systems
An analogous effect to covalent binding is believed to occur in some nuclear systems, with the difference that the shared fermions are quarks rather than electrons. High energy proton-proton scattering cross-section indicates that quark interchange of either u or d quarks is the dominant process of the nuclear force at short distance. In particular, it dominates over the Yukawa interaction where a meson is exchanged. Therefore, covalent binding by quark interchange is expected to be the dominating mechanism of nuclear binding at small distance when the bound hadrons have covalence quarks in common.

title: Covalent bond


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Condensation polymer

In polymer chemistry, condensation polymers are any kind of polymers whose process of polymerization involves a condensation reaction (i.e. a small molecule, such as water or methanol, is produced as a byproduct). Natural proteins as well as some common plastics such as nylon and PETE are formed in this way. Condensation polymers are formed by polycondensation, when the polymer is formed by condensation reactions between species of all degrees of polymerization, or by condensative chain polymerization, when the polymer is formed by sequential addition of monomers to an active site in a chain reaction. The main alternative forms of polymerization are chain polymerization and polyaddition, both of which give addition polymers.

Condensation polymerization is a form of step-growth polymerization. Linear polymers are produced from bifunctional monomers, i.e. compounds with two reactive end-groups. Common condensation polymers include polyesters, polyamides such as nylon, polyacetals, and proteins.

Polyamides
One important class of condensation polymers are polyamides. They arise from the reaction of carboxylic acid and an amine. Examples include nylons and proteins. When prepared from amino-carboxylic acids, e.g. amino acids, the stoichiometry of the polymerization includes co-formation of water:
 * n H2N-X-CO2H →  [HN-X-C(O)]n  +  (n-1) H2O

When prepared from diamines and dicarboxylic acids, e.g. the production of nylon 66, the polymerization produces two molecules of water per repeat unit:
 * n H2N-X-NH2 + n HO2C-Y-CO2H →  [HN-X-NHC(O)-Y-C(O)]n  +  (2n-1) H2O
 * [[Image:Condensation polymerization diacid diamine.svg|thumb|left|400px|General chemical structure of one type of condensation polymer]]

Polyesters
Another important class of condensation polymers are polyesters. They arise from the reaction of a carboxylic acid and an alcohol. An example is polyethyleneterephthalate, the common plastic PETE (recycling #1 in the USA):
 * n HO-X-OH + n HO2C-Y-CO2H →  [O-X-O2C-Y-C(O)]n  +  (2n-1) H2O

Safety and environmental considerations
Condensation polymers tend to be more biodegradable than addition polymers. The peptide or ester bonds between monomers can be hydrolysed, especially in the presence of catalysts or bacterial enzymes.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: Condensation polymer


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Timeline of computing

Timeline of computing presents events in the history of computing organized by year and grouped into six topic areas: predictions and concepts, first use and inventions, hardware systems and processors, operating systems, programming languages, and new application areas.

Detailed computing timelines: before 1950, 1950–1979, 1980–1989, 1990–1999, 2000–2009, 2010–2019, 2020–present

Resources

 * Stephen White, A Brief History of Computing
 * The Computer History in time and space, Graphing Project, an attempt to build a graphical image of computer history, in particular operating systems.

title: Timeline of computing


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Colorado Springs, Colorado

Colorado Springs is a city in and the county seat of El Paso County, Colorado, United States. It is the most populous city in El Paso County, with a population of 478,961 at the 2020 census, a 15.02% increase since 2010. Colorado Springs is the second-most populous city and the most extensive city in the state of Colorado, and the 39th-most-populous city in the United States. It is the principal city of the Colorado Springs metropolitan area, which had 755,105 residents in 2020, and the second-most prominent city of the Front Range Urban Corridor. It is located in east-central Colorado on Fountain Creek, 70 mi south of Denver.

At 6035 ft the city stands over 1 mi above sea level. Colorado Springs is near the base of Pikes Peak, which rises 4302.31 m above sea level on the eastern edge of the Southern Rocky Mountains. The city is the largest city north of Mexico above 6000 feet in elevation.

History
The Ute, Arapaho and Cheyenne peoples were the first recorded inhabiting the area which would become Colorado Springs. Part of the territory included in the United States' 1803 Louisiana Purchase, the current city area was designated part of the 1854 Kansas Territory. In 1859, after the first local settlement was established, it became part of the Jefferson Territory on October 24 and of El Paso County on November 28. Colorado City at the Front Range confluence of Fountain and Camp creeks was "formally organized on August13, 1859" during the Pikes Peak Gold Rush. It served as the capital of the Colorado Territory from November 5, 1861, until August 14, 1862, when the capital was moved to Golden, before it was finally moved to Denver in 1867. So many immigrants from England had settled in Colorado Springs by the early 1870s that Colorado Springs was locally referred to as "Little London." In 1871 the Colorado Springs Company laid out the towns of La Font (later called Manitou Springs) and Fountain Colony, upstream and downstream respectively, of Colorado City. Within a year, Fountain Colony was renamed Colorado Springs and officially incorporated. The El Paso County seat shifted from Colorado City in 1873 to the Town of Colorado Springs. On December 1, 1880, Colorado Springs expanded northward with two annexations.

The second period of annexations was during 1889–90, and included Seavey's Addition, West Colorado Springs, East End, and another North End addition. In 1891 the Broadmoor Land Company built the Broadmoor suburb, which included the Broadmoor Casino, and by December 12, 1895, the city had "four Mining Exchanges and 275 mining brokers." By 1898, the city was designated into quadrants by the north-south Cascade Avenue and the east-west Washington/Pikes Peak avenues.

From 1899 to 1901 Tesla Experimental Station operated on Knob Hill, and aircraft flights to the Broadmoor's neighboring fields began in 1919. Alexander Airport north of the city opened in 1925, and in 1927 the original Colorado Springs Municipal Airport land was purchased east of the city.

The city's military presence began during World War II, beginning with Camp Carson (now the 135,000-acre Fort Carson base) that was established in 1941. During the war, the United States Army Air Forces leased land adjacent to the municipal airfield, naming it Peterson Field in December 1942.

In November 1950, Ent Air Force Base was selected as the Cold War headquarters for Air Defense Command (ADC). The former WWII Army Air Base, Peterson Field, which had been inactivated at the end of the war, was re-opened in 1951 as a U.S. Air Force base. North American Aerospace Defense Command (NORAD) was established as a hardened command and control center within the Cheyenne Mountain Complex during the Cold War.

Between 1965 and 1968, the University of Colorado Colorado Springs, Pikes Peak State College and Colorado Technical University were established in or near the city. In 1977 most of the former Ent AFB became a US Olympic training center. The Libertarian Party was founded within the city in the 1970s.

On October 1, 1981, the Broadmoor Addition, Cheyenne Canon, Ivywild, Skyway, and Stratton Meadows were annexed after the Colorado Supreme Court "overturned a district court decision that voided the annexation". Further annexations expanding the city include the Nielson Addition and Vineyard Commerce Park Annexation in September 2008.

On June 23, 2012, the Waldo Canyon fire began 4 mi northwest of the city. The fire ended up destroying 347 homes and killing two people in the city. In total, over 32,000 residents had to be evacuated. At the time the fire was the most destructive in state history until it was surpassed by the Black Forest Fire the following year.

Geography
The city lies in a semi-arid Steppe climate region with the Southern Rocky Mountains to the west, the Palmer Divide to the north, high plains further east, and high desert lands to the south when leaving Fountain and approaching Pueblo. Colorado Springs is 69 mile or one hour and five minutes south of Denver by car using I-25.

Colorado Springs has the greatest total area of any municipality in Colorado. At the 2020 United States Census, the city had a total area of 507.019 km2 including 0.937 km2 of water.

Climate

Colorado Springs has a cooler, dry-winter semi-arid climate (Köppen BSk), and its location just east of the Rocky Mountains affords it the rapid warming influence from chinook winds during winter but also subjects it to drastic day-to-day variability in weather conditions. The city has abundant sunshine year-round, averaging 243 sunny days per year, and receives approximately 16.5 in of annual precipitation. Due to unusually low precipitation for several years after flooding in 1999, Colorado Springs enacted lawn water restrictions in 2002. These were lifted in 2005 but permanently reinstated in December 2019.

Colorado Springs is one of the most active lightning strike areas in the United States. This natural phenomenon led Nikola Tesla to select Colorado Springs as the preferred location to build his lab and study electricity.

Seasonal climate
December is typically the coldest month, averaging 30.8 °F. Historically, January had been the coldest month, but, in recent years, December has had both lower daily maxima and minima. Typically, there are 5.2 nights with sub-0 °F lows and 23.6 days where the high does not rise above freezing.

Snowfall is usually moderate and remains on the ground briefly because of direct sun, with the city receiving 38 in per season, although the mountains to the west often receive in excess of triple that amount; March is the snowiest month in the region, both by total accumulation and number of days with measurable snowfall. In addition, 8 of the top 10 heaviest 24-hour snowfalls have occurred from March to May. Summers are warm, with July, the warmest month, averaging 70.9 °F, and 18 days of 90 °F+ highs annually. Due to the high elevation and aridity, nights are usually relatively cool and rarely does the low remain above 70 °F. Dry weather generally prevails, but brief afternoon thunderstorms are common, especially in July and August when the city receives the majority of its annual rainfall, due to the North American monsoon.

The first autumn freeze and the last freeze in the spring, on average, occur on October 2 and May 6, respectively; the average window for measurable snowfall (≥0.1 in) is October 21 through April 25. Extreme temperatures range from 101 °F on June 26, 2012 and most recently on June 21, 2016, down to -27 °F on February 1, 1951, and December 9, 1919.

Demographics

As of the 2020 United States Census, the population of the City of Colorado Springs was 478,961 (40th most populous U.S. city), the population of the Colorado Springs Metropolitan Statistical Area was 755,105 (79th most populous MSA), and the population of the Front Range Urban Corridor was 5,055,344.

2020 census
As of the April 2010 census, 78.8% of the population of the city was White (non-Hispanic Whites were 70.7% of the population, compared with 86.6% in 1970 ), 16.1% Hispanic or Latino of any race (compared with 7.4% in 1970), 6.3% Black or African American, 3.0% Asian, 1.0% descended from indigenous peoples of the Americas, 0.3% descended from indigenous Hawaiians and other Pacific islanders, 5.5% of some other race, and 5.1% of two or more races. Mexican Americans made up 14.6% of the city's population, compared with 9.1% in 1990. The median age in the city was 35 years.

Economy
Colorado Springs's economy is driven primarily by the military, the high-tech industry, and tourism, in that order. The city is experiencing growth in the service sectors. In June 2019, before the COVID-19 pandemic, the unemployment rate was 3.3%. The state's unemployment rate in June 2022 was 3.4% compared to 3.6% for the nation.

Military

, there are nearly 45,000 active-duty troops in Colorado Springs. There are more than 100,000 veterans and thousands of reservists. The military and defense contractors supply more than 40% of the Pikes Peak region's economy.

Colorado Springs is home to the Peterson Space Force Base, Schriever Space Force Base, Cheyenne Mountain Space Force Station, U.S. Space Command, and Space Operations Command— the largest contingent of space service military installations. They are responsible for intelligence gathering, space operations, and cyber missions.

Peterson Space Force Base is responsible for the North American Aerospace Defense Command (NORAD) and the United States Northern Command (USNORTHCOM) headquarters, Space Operations Command, and Space Deltas 2, 3, and 7. Located at Peterson is the 302nd Airlift Wing, an Air Force Reserve unit, that transports passengers and cargo and fights wildfires.

Schriever Space Force Base is responsible for Joint Task Force-Space Defense and Space Deltas 6, 8, and 9. The NORAD and USNORTHCOM Alternate Command Center is located at the Cheyenne Mountain Complex. Within the mountain complex, the Cheyenne Mountain Space Force Station has been operated by Space Operations Command. On January 13, 2021, the Air Force announced a new permanent home for Space Command, moving it from Colorado Springs to Huntsville, Alabama in 2026, but the decision could be reversed by Congress.

Army divisions are trained and stationed at Fort Carson. The United States Air Force Academy was established after World War II, on land donated by the City of Colorado Springs.

Defense industry
The defense industry forms a significant part of the Colorado Springs economy, with some of the city's largest employers being defense contractors. Some defense corporations have left or downsized city campuses, but slight growth has been recorded. Significant defense corporations in the city include Northrop Grumman, Boeing, General Dynamics, L3Harris Technologies, SAIC, ITT, Lockheed Martin, and Bluestaq. The Space Foundation is based in Colorado Springs.

High-tech industry
A large percentage of Colorado Springs's economy is still based on manufacturing high-tech and complex electronic equipment. The high-tech sector in the Colorado Springs area has decreased its overall presence from 2000 to 2006 (from around 21,000 to around 8,000), with notable reductions in information technology and complex electronic equipment. Current trends project the high-tech employment ratio will continue to decrease.

High-tech corporations offering fibre-optics to the premises connections within the city include: Lumen Technologies, Comcast and other providers as of 2023. Hewlett-Packard still has some sales, support, and SAN storage engineering center for the computer industry. Storage Networking Industry Association is the home of the SNIA Technology Center. Keysight Technologies, spun off in 2014 from Agilent, which was itself spun off from HP in 1999 as an independent, publicly traded company, has its oscilloscope research and development division based in Colorado Springs. Intel had 250 employees in 2009. The Intel facility is now used for the centralized unemployment offices, social services, El Paso county offices, and a bitcoin mining facility. Microchip Technology (formerly Atmel), is a chip fabrication organization. The Apple Inc. facility was sold to Sanmina-SCI in 1996.

Tourism
Almost immediately following the arrival of railroads beginning in 1871, the city's location at the base of Pikes Peak and the Rocky Mountains made it a popular tourism destination. Tourism is the third largest employer in the Pikes Peak region, accounting for more than 16,000 jobs. In 2018, 23 million day and overnight visitors came to the area, contributing $2.4 billion in revenue.

Colorado Springs has more than 55 attractions and activities in the area, including Garden of the Gods park, United States Air Force Academy, the ANA Money Museum, Cheyenne Mountain Zoo, Colorado Springs Fine Arts Center at Colorado College, Old Colorado City, The National Museum of World War II Aviation, and the U.S. Olympic & Paralympic Training Center. In 2020, the United States Olympic & Paralympic Museum opened; the Flying W Ranch Chuckwagon Dinner & Western Show reopened in 2020. A new Pikes Peak Summit Complex opened at the 14,115-foot summit in 2021. The Manitou and Pikes Peak Railway also reopened in 2021.

The downtown Colorado Springs Visitor Information Center offers free area information to leisure and business travelers. The Cultural Office of the Pikes Peak Region (COPPeR), also downtown, supports and advocates for the arts throughout the Pikes Peak Region. It operates the PeakRadar website to communicate city events.

Annual cultural events
Colorado Springs is home to the annual Colorado Springs Labor Day Lift Off, a hot air balloon festival that takes place over Labor Day weekend at the city's Memorial Park.

Other annual events include: a comic book convention and science fiction convention called GalaxyFest in February, a pride parade called PrideFest in July, the Greek Festival, the Pikes Peak Ascent and Marathon, and the Steers & Beers Whiskey and Beer Festival in August,  and the Emma Crawford Coffin Races and Festival in nearby Manitou Springs and Arts Month in October.

The Colorado Springs Festival of Lights Parade is held the first Saturday in December. The parade is held on Tejon Street in Downtown Colorado Springs.

Breweries
In 2017, Colorado had the third-most craft breweries at 348. Breweries and microbreweries have become popular in Colorado Springs, which hosts over 30 of them.

Religious institutions

Although houses of worship of almost every major world religion are within the city, Colorado Springs has in particular attracted a large influx of Evangelical Christians and Christian organizations in recent years. At one time Colorado Springs was the national headquarters for 81 different religious organizations, earning the city the tongue-in-cheek nicknames "the Evangelical Vatican" and "The Christian Mecca."

Religious groups with regional or international headquarters in Colorado Springs include:

 * Association of Christian Schools International
 * Biblica
 * Children's HopeChest
 * Community Bible Study
 * Compassion International
 * David C. Cook/Integrity Music
 * Development Associates International
 * Engineering Ministries International
 * Family Talk
 * Focus on the Family
 * Global Action
 * HCJB
 * Hope & Home
 * The Navigators
 * One Child Matters
 * Roman Catholic Diocese of Colorado Springs
 * VisionTrust
 * WayFM Network
 * Young Life

Marijuana
Although Colorado voters approved Colorado Amendment 64, a constitutional amendment in 2012 legalizing retail sales of marijuana for recreational purposes, the Colorado Springs city council voted not to permit retail shops in the city, as was allowed in the amendment. Medical marijuana outlets continue to operate in Colorado Springs. In 2015, there were 91 medical marijuana clinics in the city, which reported sales of $59.6 million in 2014, up 11 percent from the previous year but without recreational marijuana shops. On April 26, 2016, Colorado Springs city council decided to extend the current six-month moratorium to eighteen months with no new licenses to be granted until May 2017. A scholarly paper suggested the city would give up $25.4 million in tax revenue and fees if the city continued to thwart the industry from opening within the city limits. As of March 1, 2018, there were 131 medical marijuana centers and no recreational cannabis stores. As of 2019 Colorado Springs is still one of seven towns that have only allowed for medical marijuana.

In popular culture
Colorado Springs has been the subject of or setting for many books, films and television shows, and is a frequent backdrop for political thrillers and military-themed stories because of its many military installations and vital importance to the United States' continental defense. Notable television series using the city as a setting include Dr. Quinn, Medicine Woman, Homicide Hunter and the Stargate series Stargate SG-1, as well as the films WarGames, The Prestige, and BlacKkKlansman.

In a North Korean propaganda video released in April 2013, Colorado Springs was singled out as one of four targets for a missile strike. The video failed to pinpoint Colorado Springs on the map, instead showing a spot somewhere in Louisiana.

Olympic sports

Colorado Springs, dubbed Olympic City USA, is home to the United States Olympic & Paralympic Training Center and the headquarters of the United States Olympic & Paralympic Committee and the United States Anti-Doping Agency.

Further, over 50 national sports organizations (non-Olympic) headquarter in Colorado Springs. These include the National Strength and Conditioning Association, Sports Incubator, a various non-Olympic Sports (such as USA Ultimate), and more.

Colorado Springs and Denver hosted the 1962 World Ice Hockey Championships.

The city has a long association with the sport of figure skating, having hosted the U.S. Figure Skating Championships six times and the World Figure Skating Championships five times. It is home to the World Figure Skating Museum and Hall of Fame and the Broadmoor Skating Club, a notable training center for the sport. In recent years, the Broadmoor World Arena has hosted skating events such as Skate America and the Four Continents Figure Skating Championships.

Baseball
Colorado Springs is home to a professional baseball team, The Rocky Mountain Vibes who are a member of the Pioneer League an MLB Partner League

Pikes Peak International Hill Climb
The Pikes Peak International Hill Climb (PPIHC), also known as The Race to the Clouds, is an annual invitational automobile and motorcycle hill climb to the summit of Pikes Peak, every year on the last Sunday of June. The highway wasn't completely paved until 2011.

Local collegiate teams
The local colleges feature many sports teams. Notable among them are several nationally competitive NCAA Division I teams: United States Air Force Academy (Falcons) Football, Basketball and Hockey and Colorado College (Tigers) Hockey, and Women's Soccer.

Rodeo
Colorado Springs was the original headquarters of the Professional Bull Riders (PBR) from its founding in 1992 until 2005, when the organization was moved to Pueblo.

Parks, trails and open space
The city's Parks, Recreation and Cultural Services manage 136 neighborhood parks, eight community parks, seven regional parks, and five sports complexes, totaling 9000 acre. They also manage 500 acre of trails, of which 160 mile are park trails and 105 miles are urban. There are 5000 acre of open space in 48 open-space areas.

Parks
Garden of the Gods is on Colorado Springs's western edge. It is a National Natural Landmark, with 300 foot red/orange sandstone rock formations often viewed against a backdrop of the snow-capped Pikes Peak. This park is free to the public and offers many recreational opportunities, such as hiking, rock climbing, cycling, horseback riding and tours. It offers a variety of annual events, one of the most popular of which is the Starlight Spectacular, a recreational bike ride held every summer to benefit the Trails and Open Space Coalition of Colorado Springs.

Colorado Springs has several major city parks, such as Palmer Park, America the Beautiful Park in downtown, Memorial Park, which includes many sports fields, an indoor swimming pool and skating rink, a skateboard bowl and two half-pipes, and Monument Valley Park, which has walking and biking paths, an outdoor swimming pool and pickleball courts. Monument Valley Park also has Tahama Spring, the original spring in Colorado Springs. Austin Bluffs Park affords a place of recreation in eastern Colorado Springs. El Paso County Regional Parks include Bear Creek Regional Park, Bear Creek Dog Park, Fox Run Regional Park and Fountain Creek Regional Park and Nature Center. Ponderosa pine (Pinus ponderosa), Gambel oak (Quercus gambelii),  narrowleaf yucca (Yucca angustissima, syn. Yucca glauca) and prickly pear cactus (Opuntia macrorhiza).

Trails
Three trails, the New Santa Fe Regional Trail, Pikes Peak Greenway and Fountain Creek Regional Trail, form a continuous path from Palmer Lake, through Colorado Springs, to Fountain, Colorado. The majority of the trail between Palmer Lake and Fountain is a soft surface breeze gravel trail. A major segment of the trail within the Colorado Springs city limits is paved. The trails, except Monument Valley Park trails, may be used for equestrian traffic. Motorized vehicles are not allowed on the trails. Many of the trails are interconnected, having main spine trails, like the Pikes Peak Greenway, that lead to secondary trails.

Government
On November 2, 2010, Colorado Springs voters adopted a council-strong mayor form of government. The City of Colorado Springs transitioned to the new system of government in 2011. Under the council-strong mayor system of government, the mayor is the chief executive and the city council is the legislative branch. The mayor is a full-time elected position and not a member of the council. The council has nine members, six of whom represent one of six equally populated districts each. The remaining three members are elected at-large.

Colorado Springs City Hall was built from 1902 to 1904 on land donated by W. S. Stratton.

City Council
The Colorado Springs City Council consists of nine elected officials, six of whom represent districts and three of whom represent the city at-large.

 * District 1 – Dave Donelson
 * District 2 – Randy Helms – Council President
 * District 3 – Michelle Talarico
 * District 4 – Yolanda Avila
 * District 5 – Nancy Henjum
 * District 6 – Mike O'Malley
 * At-large – Lynette Crow-Iverson – Council President Pro Tem
 * At-large – David Leinweber
 * At-large – Brian Risley

Politics
In 2017 Caleb Hannan wrote in Politico that Colorado Springs was "staunchly Republican", "a right-wing counterweight to liberal Boulder", and that a study ranked it "the fourth most conservative city in America". In 2016 Hannan wrote that downtown Colorado Springs had a different political vibe from the overall area's and that there were "superficial signs of changing demographics". Since 2020, Colorado Springs has continued to shift towards the political center. In 2022, Governor Jared Polis won the city in his bid for reelection. In the 2023 mayoral election, independent candidate Yemi Mobolade handily won the race and became the first elected non-Republican mayor of the city.

Primary and secondary education
Public schools The public education in the city is divided into several school districts:
 * Colorado Springs School District 11 (center of the city)
 * Academy School District 20 (north end)
 * Falcon School District 49 (east side)
 * Widefield School District 3 (south end)
 * Fountain-Fort Carson School District 8 (far south end)
 * Harrison School District 2 (south central area)
 * James Irwin Charter High School (east central area)
 * Cheyenne Mountain School District 12 (southwest corner)
 * The Vanguard School, CIVA Charter High School and The Classical Academy are charter schools.

Private schools
 * Roman Catholic Diocese of Colorado Springs schools including within the boundaries of the city
 * Corpus Christi Catholic School – PreK-8
 * Divine Redeemer Catholic School – PreK-8
 * St. Gabriel Classical Academy – PreK-3
 * St. Paul Catholic School – PreK-8
 * St. Mary's High School – an independent Catholic high school
 * Fountain Valley School of Colorado – a residential high school established in 1930 with a current enrollment of about 240.
 * The Colorado Springs School – a preK-12 school established in 1962 with a current enrollment of about 300.
 * Colorado Springs Christian Schools – A PreK–12th grade Christian school with two campuses started in 1972 and with an enrollment of about 1,150 in 2021.
 * Evangelical Christian Academy – a preK-12 school established in 1971 with a current enrollment of about 350.
 * Pikes Peak Christian School – a preK-12 Christian school with a current enrollment of about 210

In addition the state of Colorado runs the Colorado School for the Deaf and Blind, a residential school for people up to age 21 and established in 1874, in the city.

Higher education

State institutions offering bachelors and graduate degree programs in Colorado Springs include the University of Colorado at Colorado Springs (UCCS) with more than 12,000 students, and, Pikes Peak State College which offers mostly two-year degree associate degrees. The United States Air Force Academy is a federal institution offering bachelor's degrees for officer candidates.

Private non-profit institutions include Colorado College established in 1874 with about 2,000 undergraduates. Colorado Christian University has its Colorado Springs Center in the city.

Private for-profit institutions include Colorado Technical University whose main campus is in Colorado Springs and IntelliTec College a technical training school.

Interstate highways
Colorado Springs is primarily served by one interstate highway. I-25 runs north and south through Colorado, and traverses the city for nearly 18 mi, entering the city south of Circle Drive and exiting north of North Gate Boulevard. In El Paso County it is known as Ronald Reagan Highway.

State and U.S. highways
A number of state and U.S. highways serve the city. State Highway 21 is a major east side semi-expressway from Black Forest to Fountain, known locally and co-signed as Powers Boulevard. State Highway 83 runs north–south from central Denver to northern Colorado Springs. State Highway 94 runs east–west from western Cheyenne County to eastern Colorado Springs where it terminates at US 24. US 24 is a major route through the city and county, providing access to Woodland Park via Ute Pass to the west and downtown, Nob Hill and numerous suburbs to the east. It is co-signed with Platte Ave after SH 21 and originally carried local traffic through town. The Martin Luther King Jr Bypass runs from I-25 near Circle Drive along Fountain Blvd to SH 21, then east again. State Highway 115 begins in Cañon City, traveling north along the western edge of Fort Carson; when it reaches the city limits it merges with Nevada Avenue, a signed Business Route of US 85. US 85 and SH 115 are concurrent between Lake Avenue and I-25. US 85 enters the city at Fountain and was signed at Venetucci Blvd, Lake Avenue, and Nevada Avenue at various points in history; however most of US 85 is concurrent with I-25 and is not signed.

County and city roads
In November 2015, voters in Colorado Springs overwhelmingly passed ballot measure 2C, dedicating funds from a temporary sales tax increase to much needed road and infrastructure improvements over five years. This temporary increase is estimated to bring in approximately $50 million annually, which will be used solely to improve roads and infrastructure. The ballot measure passed by a margin of approximately 65–35%.

In 2004, the voters of Colorado Springs and El Paso County established the Pikes Peak Rural Transportation Authority.

In early 2010, the city of Colorado Springs approved an expansion of the northernmost part of Powers Boulevard to create an Interstate 25 bypass commonly referred to as the Copper Ridge Expansion.

Airport
Colorado Springs Airport (COS; ICAO: KCOS) has been in operation since 1925. It is the second-largest commercial airport in the state, after Denver International Airport (DEN; ICAO: KDEN). It covers 7,200 acre of land at an elevation of approximately 6200 ft. COS is considered to be a joint-use civilian and military airport, as Peterson Space Force Base is a tenant of the airport. It has three paved runways: 17L/35R is 13,501 by, the runway 17R/35L is 11022 by and the runway 13/31 is 8270 by. The airport handled 2,134,618 passengers in 2022, and is served by American, Avelo, Delta, Southwest, Sun Country, and United.

Railroads
Freight service is provided by Union Pacific and BNSF.

Once an important hub, the city was once served by four Class 1 railroads, as well as a number of smaller operators, some of which were narrow gauge, and an extensive streetcar system, the Colorado Springs and Interurban Railway.

Currently there is no intercity passenger service; the last remaining services connecting the Front Range cities ceased with the formation of Amtrak in 1971. Front Range Passenger Rail is a current proposal (as of 2023) to link the cities from Pueblo in the south, north to Fort Collins and possibly Cheyenne, Wyoming.

Bicycling
In April 2018, the Colorado Springs City Council approved a Bike Master Plan. The vision of the city's Bike Master Plan is "a healthy and vibrant Colorado Springs where bicycling is one of many transportation options for a large portion of the population, and where a well-connected and well-maintained network of urban trails, single-track, and on-street infrastructure offers a bicycling experience for present and future generations that is safe, convenient, and fun for getting around, getting in shape, or getting away." Bike lanes in Colorado Springs have not been deployed without controversy. According to The Gazette, their readers "have mixed feelings for new bike lanes." In December 2016, the City removed a bike lane along Research Parkway due to overwhelming opposition; an online survey found that 80.5% of respondents opposed the bike lane. The Gazette has stated that since the Bike Master Plan was adopted by city council, "no issue has elicited more argument in The Gazette pages," and due to this immense public interest, on February 25, 2019, The Gazette hosted a town hall meeting called "Battle of the Bike Lanes."

Walkability
A 2011 study by Walk Score ranked Colorado Springs 34th most walkable of fifty largest U.S. cities.

Mountain Metropolitan Transit
Mountain Metropolitan Transit (MMT) is testing Battery Electric Buses (BEB), and if the buses perform well, the agency plans to acquire its first three BEBs in 2021 using funds from the Volkswagen emissions scandal and resulting lawsuit and settlement. On April 22, 2022, Mountain Metro unveiled four new all-electric Proterra ZX5 buses to be added to their fleet. The new buses join their current fleet of 67 clean diesel buses. They are funded by the Colorado Department of Transportation Division of Transit and Rail Settlement Transit Bus Replacement Program, Volkswagen Diesel Emission Settlement trust, and Federal transit Administration 5339(b) Buses and Bus Facilities Program grant. The Proterra ZX5 buses run 220 to 330 miles on a single charge, and cost $1.2 million per bus.

Mountain Metro Mobility
Mountain Metro Mobility is an Americans with Disabilities Act (ADA) federally mandated complementary ADA paratransit service, which provides demand-response service for individuals with mobility needs that prevent them from using the fixed-route bus system.

Mountain Metro Rides
Mountain Metro Rides offers alternative transportation options to residents of the Pikes Peak Region. The program is designed to reduce congestion and pollution by encouraging people to commute by carpool, vanpool, bicycling or walking.

Neighborhoods and Historic Places

 * Anderosa Neighborhood
 * Banning Lewis Ranch Neighborhood
 * Black Forest Neighborhood
 * Boulder Crescent Place Historic District
 * Briargate Neighborhood
 * Broadmoor Neighborhood
 * Broadmoor Bluffs Neighborhood
 * Broadmoor Hills Neighborhood
 * Broadmoor Oaks Neighborhood
 * Cheyenne Hills Neighborhood
 * Cimarron Hills Neighborhood
 * Clearview Estates Neighborhood
 * Colorado Centre Neighborhood
 * Columbine Estates Neighborhood
 * Cragmor Neighborhood
 * Deerfield Hills Neighborhood
 * Discovery Neighborhood
 * Divine Redeemer Neighborhood
 * Downtown
 * Eastborough Neighborhood
 * Falcon Estates Neighborhood
 * Fountain Valley Ranch Neighborhood
 * Garden Ranch Neighborhood
 * Gateway Park Neighborhood
 * Gleneagle Neighborhood
 * Historic Uptown Neighborhood
 * Holland Park Neighborhood
 * Indian Heights Neighborhood
 * Interquest Neighborhood
 * Ivywild Neighborhood
 * Kettle Creek Neighborhood
 * Kissing Camels Neighborhood
 * Knob Hill Neighborhood
 * Lowell Neighborhood
 * Manitou Springs
 * Mesa Neighborhood
 * Middle Creek Neighborhood
 * Middle Shooks Run Neighborhood
 * Mountain Shadows Neighborhood
 * Northgate Neighborhood
 * Norwood Neighborhood
 * Oak Hills Neighborhood
 * Oak Valley Ranch Neighborhood
 * Old Colorado City
 * Old Farm Neighborhood
 * Old North End Historic District
 * Park Hill Neighborhood
 * Patty Jewett Neighborhood
 * Papeton/Venetian Village Neighborhood
 * Peregrine Neighborhood
 * Pheasant Run Ranch Neighborhood
 * Pikes Peak Park Neighborhood
 * Pikeview/Pinecliff Neighborhood
 * Pine Creek Neighborhood
 * Pinon Valley Neighborhood
 * Pulpit Rock Neighborhood
 * Ridgeview Neighborhood
 * Rockrimmon Neighborhood
 * Roswell Neighborhood
 * Rustic Hills Neighborhood
 * Security
 * Shooks Run Neighborhood
 * Southborough Neighborhood
 * Stetson Hills Neighborhood
 * Spring Creek Neighborhood
 * Springs Ranch Neighborhood
 * Stratmoor Hills Neighborhood
 * Stratmoor Valley Neighborhood
 * Stratton Meadows Neighborhood
 * Sundown Neighborhood
 * Trailridge Neighborhood
 * Wagon Trails Neighborhood
 * Weber-Wahsatch Historic District
 * Widefield
 * Wolf Ranch Neighborhood
 * Venetian Village Neighborhood
 * Villa Loma Neighborhood
 * Village Seven Neighborhood

See also National Register of Historic Places in Colorado Springs, Colorado

Sister cities
Colorado Springs' sister cities are:
 * 🇯🇵 Fujiyoshida, Yamanashi, Japan (1962)
 * 🇹🇼 Kaohsiung, Taiwan (1983)
 * 🇰🇬 Bishkek, Kyrgyzstan (1994)
 * 🇲🇽 Nuevo Casas Grandes, Chihuahua, Mexico (1996)
 * 🇦🇺 Canterbury-Bankstown, Sydney, Australia (1999)
 * 🇬🇷 Olympia, Peloponnese, Greece (2014)
 * Suspended sistership
 * 🇷🇺 Smolensk, Smolensk Oblast, Russia (1993–2022)

Colorado Springs's sister city organization began when it became partners with Fujiyoshida. The torii gate erected to commemorate the relationship stands at the corner of Bijou Street and Nevada Avenue, and is one of the city's most recognizable landmarks. The torii gate, crisscrossed bridge and shrine, in the median between Platte and Bijou Streets downtown, were a gift to Colorado Springs, erected in 1966 by the Rotary Club of Colorado Springs to celebrate the friendship between the two communities. A plaque near the torii gate states that "the purpose of the sister city relationship is to promote understanding between the people of our two countries and cities". The Fujiyoshida Student exchange program has become an annual event.

In 2006 and 2010, the Bankstown TAP (Talent Advancement Program) performed with the Youth Symphony and the Colorado Springs Children's Chorale as part of the annual "In Harmony" program. A notable similarity between Colorado Springs and its sister cities is their geographic positions: three of the seven cities are near the foot of a major mountain or mountain range, as is Colorado Springs.

title: Colorado Springs, Colorado