Chlorine

Chlorine, ₁₇Cl
General properties
Pronunciation	/ˈklɔːriːn, -aɪn/ (KLOHR-een, --eyen)
Appearance	pale yellow-green gas
Standard atomic weight (Ar, standard)	[35.446, 35.457] conventional: 35.45
Chlorine in the periodic table
	sulfur ← chlorine → argon
Atomic number (Z)	17
Group	group 17 (halogens)
Period	period 3
Block	p-block
Element category	reactive nonmetal
Electron configuration	[Ne] 3s2 3p5
Electrons per shell	2, 8, 7
Physical properties
Phase at STP	gas
Melting point	171.6 K (−101.5 °C, −150.7 °F)
Boiling point	239.11 K (−34.04 °C, −29.27 °F)
Density (at STP)	3.2 g/L
when liquid (at b.p.)	1.5625 g/cm3
Critical point	416.9 K, 7.991 MPa
Heat of fusion	(Cl2) 6.406 kJ/mol
Heat of vaporization	(Cl2) 20.41 kJ/mol
Molar heat capacity	(Cl2); 33.949 J/(mol·K)
Atomic properties
Oxidation states	−1, +1, +2, +3, +4, +5, +6, +7 (a strongly acidic oxide)
Electronegativity	Pauling scale: 3.16
Ionization energies	1st: 1251.2 kJ/mol ; 2nd: 2298 kJ/mol ; 3rd: 3822 kJ/mol ; (more) ;
Covalent radius	102±4 pm
Van der Waals radius	175 pm
	Spectral lines of chlorine
Other properties
Natural occurrence	primordial
Crystal structure	orthorhombic
Speed of sound	206 m/s (gas, at 0 °C)
Thermal conductivity	8.9×10−3 W/(m·K)
Electrical resistivity	>10 Ω·m (at 20 °C)
Magnetic ordering	diamagnetic
Magnetic susceptibility	−40.5·10−6 cm3/mol
CAS Number	(Cl2) 7782-50-5
History
Discovery and first isolation	Carl Wilhelm Scheele (1774)
Recognized as an element by	Humphry Davy (1808)
Main isotopes of chlorine
ε	36S
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Chlorine (chemical symbol Cl) is a chemical element. Its atomic number (which is the number of protons in it) is 17, and its atomic mass is 35.45. It is part of the 7th column (halogens) on the periodic table of elements.

Chlorine gas in a tube

PropertiesEdit

Physical propertiesEdit

Chlorine is a very irritating and greenish-yellow gas. It has a strong smell like bleach. It is toxic. It can be made into a liquid when cooled. It is heavier than air.

Chemical propertiesEdit

Chlorine is highly reactive. It is more reactive than bromine but less reactive than fluorine. It reacts with most things to make chlorides. It can even burn things instead of oxygen. It dissolves in water to make a mixture of hypochlorous acid and hydrochloric acid. The more acidic it is, the more chlorine is made; the more basic it is, the more hypochlorous acid (normally turned into hypochlorite) and hydrochloric acid (normally turned into chlorides) are there. Chlorine reacts with bromides and iodides to make bromine and iodine.

Chlorine compoundsEdit

Chlorine exists in several oxidation states: -1, +1, +3, +4, +5, and +7. The -1 state is most often in chloride. Chlorides are not reactive. Compounds containing chlorine in its +1 oxidation state are hypochlorites. Only one is common. They are a strong oxidizing agent, as are all + oxidation state compounds. +3 is in chlorites. +4 is in chlorine dioxide, a common chlorine compound that is not a chloride. +5 is in chlorates. +7 is in perchlorates. Hypochlorites are most reactive, while perchlorates are the least reactive.

Many organic compounds have chlorine in them. Freon has chlorine in it. PVC (Poly-vinyl chloride), a common plastic, has chlorine in it.

Chlorine oxides can be made, but most of them are very reactive and unstable.

PVC pipe, a plastic that has chlorine in it
Sodium chloride
Potassium chlorate
Potassium perchlorate

OccurrenceEdit

Chlorine is not found as an element. Sodium chloride is the most common chlorine ore. It is in the ocean (sea salt) and in the ground (rock salt). There are some organic compounds that have chlorine in them, too.

PreparationEdit

It is made by electrolysis (the passing of electricity through a solution to make chemical reactions happen) of sodium chloride. This is known as the chloralkali process. It can also be made by reacting hydrogen chloride with oxygen and a catalyst. It can be made in the laboratory by reacting manganese dioxide with hydrochloric acid. It is made when sodium hypochlorite reacts with hydrochloric acid. This is a dangerous reaction that can happen without anyone knowing.

UsesEdit

Chlorine is widely used to purify water (usually in a swimming pool), as a disinfectant and bleach, and in the making of many important compounds including chloroform and carbon tetrachloride. It was used as a poison gas in some wars.

HistoryEdit

It was discovered in 1774 by Carl Wilhelm Scheele who thought it had oxygen in it. Chlorine was named in 1810 by Humphry Davy who insisted it was an element. The US made all water chlorinated (added chlorine to water) by 1918.

SafetyEdit

It is poisonous in large amounts and can damage skin. When it is inhaled (breathed in), it irritates the lungs, eyes, and skin badly. It can cause fire with some things because it is very reactive. It is heavier than air, so it can fill up enclosed spaces.

Related pagesEdit

SourcesEdit

↑ Chlorine, Gas Encyclopaedia, Air Liquide
↑ Magnetic susceptibility of the elements and inorganic compounds, in Lide, D. R., ed. (2005). CRC Handbook of Chemistry and Physics (86th ed.). Boca Raton (FL): CRC Press. ISBN 0-8493-0486-5.
↑ Weast, Robert (1984). CRC, Handbook of Chemistry and Physics. Boca Raton, Florida: Chemical Rubber Company Publishing. pp. E110. ISBN 0-8493-0464-4.

[1] Chlorine, Gas Encyclopaedia, Air Liquide

[2] Magnetic susceptibility of the elements and inorganic compounds, in Lide, D. R., ed. (2005). CRC Handbook of Chemistry and Physics (86th ed.). Boca Raton (FL): CRC Press. ISBN 0-8493-0486-5.

[3] Weast, Robert (1984). CRC, Handbook of Chemistry and Physics. Boca Raton, Florida: Chemical Rubber Company Publishing. pp. E110. ISBN 0-8493-0464-4.

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