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17 Cl 35.453(2)

Chlorine

Halogen
Symbol Cl
Atomic Number 17
Atomic Weight 35.453(2)
CAS Registry ID 7782-50-5
Group Name Halogen
Period Number 3
Block p-block
State at STP Solid

Description

Sample of Chlorine ⌕ Enlarge Image

Chlorine is a halogen that is a yellow-green gas in its natural gas state. Chlorine has an atomic weight of 35.453, a melting point of - 150.7 °F, and a boiling point of - 29.27 °F. Chlorine has a strong odor, and has poisonous and toxic effects on animals. The most frequent uses of chlorine include: to produce water that is safe to drink, in the production of petroleum products, solvents, paints, plastics, paper products, and insecticides, and in the production of chlorinated cleaners, bleaches, and disinfectants.

Isolation

Chlorine in nature occurs most often in a salt form and in minerals. There are many processes that can be used to isolate elemental chlorine.

Chlorine ⌕ Enlarge Image

Large scale chlorine isolation for industrial purposes is isolated through the electrolysis of sodium chloride. Through this process, sodium chloride is dissolved in water and an electric current is passed through the solution. The resulting chemicals are elemental chlorine, hydrogen gas, and sodium hydroxide. Other isolation processes using electrolysis of chloride solutions include mercury cell electrolysis and diaphragm cell electrolysis.

Mercury cell electrolysis is the least inefficient of the chlorine isolation processes. During this process, titanium anodes are used in a sodium chloride, or potassium chloride, solution which flows over a liquid mercury cathode. The current flows releases chlorine, and the sodium, or potassium, element reacts with the mercury.

Diaphragm cell electrolysis uses an asbestos diaphragm to separate the cathode and anode. During this process the brine, or chlorine salt solution, is passed into the anode compartment and then flows through the asbestos diaphragm to the cathode compartment. Elemental chlorine forms in the anode compartment while sodium hydroxide and hydrogen form in the cathode compartment.

General

NameChlorine
SymbolCl
Number17
Chemical seriesHalogen
Group17
Period3
Blockp
Appearanceyellowish green
Standard atomic weight35.453(2) g·mol⁻¹
Electron configuration[Ne] 3s2 3p5
Electrons per shell2, 8, 7

Atomic Properties

Crystal structureorthorhombic
Oxidation states±1, 3, 5, 7 (strongly acidic oxide)
Electronegativity3.16 (Pauling scale)
Ionization energies1st: 1251.2 kJ·mol−1
2nd: 2298 kJ·mol−1
3rd: 3822 kJ·mol−1
Atomic radius100 pm
Atomic radius (calc.)79 pm
Covalent radius99 pm
Van der Waals radius175 pm

Physical Properties

Phasegas
Density (near r.t.)(0 °C, 101.325 kPa) 3.2 g/L
Liquid density at m.p.
Melting point171.6 K (-101.5 °C, -150.7 °F)
Boiling point239.11 K (-34.4 °C, -29.27 °F)
Critical point416.9 K, 7.991 MPa
Heat of fusion(Cl2) 6.406 kJ·mol−1
Heat of vaporization(Cl2) 20.41 kJ·mol−1
Heat capacity(25 °C) (Cl2) 33.949 J·mol−1·K−1

Miscellaneous

Magnetic orderingnonmagnetic
Electrical resistivity(20 °C) > 10Ω·m
Thermal conductivity(300 K) 8.9 m W·m−1·K−1
Thermal expansion
Speed of sound (thin rod)(gas, 0 °C) 206 m/s
Young's modulus
Shear modulus
Bulk modulus
Poisson ratio
Mohs hardness
Vickers hardness
Brinell hardness