Properties of the halogen elements

fluorine chlorine

atomic number 9 17

atomic weight 18.9984 35.453*

colour of element light greenish yellow greenish yellow

melting point (°C) −219.62 −100.98

boiling point (°C) −188.14 −34.05

density (760 mm Hg)

● gas (grams per litre)

1.696 (0 °C) 3.214 (0 °C)

● liquid (grams per cubic cm)

1.108 (−188 °C) 1.655 (−70 °C)

● solid (grams per cubic cm)

1.32 (−273 °C) 2.17 (−195 °C)

solubility in water (reacts) 2.3 (vol/vol 20 °C) carbon tetrachloride (reacts) 8.48 percent (by weight, 20 °C) chloroform (280 grams per 1,000 grams, 0 °C)

oxidation numbers −1 −1, +1, +3, +4, +5, +6, +7

mass number of most common isotopes (terrestrial abundance, percent) 19 (100) 35 (75.53) 37 (24.47)

radioactive isotopes (mass numbers) 17, 18, 20–22 32–34, 36, 38–40

heat of fusion (kilocalories per mole) 0.244 1.53

heat of vaporization (kilocalories per mole) 1.561 4.863

heat of hydration of the −1 ion (kilocalories per mole) 120.8 88

specific heat (kilocalories per gram per °C at 25 °C)

constant pressure 0.1842 (17 °C) 0.114

constant volume 0.0849

critical temperature (°C) −129 144

critical pressure (atmospheres) 56.8 77.3

critical density (grams per cubic cm) 0.63 0.567

crystal structure — orthorhombic

electrical resistivity (microhm-cm) — ~(10¹⁰) (near freezing point)

magnetic susceptibility (cubic cm per gram)

gas −3.4(10⁻⁷) −18.7(10⁻¹⁰) (0 °C, 760 mm Hg)

liquid −5.9(10⁻⁷) (−16 °C)

radius

ionic (angstroms) 1.33 1.81

covalent (angstroms) 0.71 0.99

bond energy (kilocalories per mole) 37.7 58.0

ionization energy (kilocalories per mole) 402 300

electron affinity (kilocalories per mole) 79.5 83.3

electronegativity (Allred-Rochow) 4.10 2.83

bromine iodine astatine

atomic number 35 53 85

atomic weight 79.904* 126.904 (210)

colour of element brown-red dark violet —

melting point (°C) −7.25 113.5 ~300

boiling point (°C) 58.8 184.4 ~370

density (760 mm Hg)

● gas (grams per litre)

5.6 (175.5 °C) 6.75 (185 °C) —

● liquid (grams per cubic cm)

3.12 (20 °C) 3.960 (120 °C) —

● solid (grams per cubic cm)

4.17 (−273 °C) 4.930 (20 °C) —

solubility in water 3.41 (grams per 100 grams, 20 °C) completely miscible 0.293 (grams per 1,000 grams) aq. iodide solution completely miscible 19.2 (grams per 1,000 grams) completely miscible 49.7 (grams per 1,000 grams) —

oxidation numbers −1, +1, +3, +4, +5, +7 −1, +1, +3, +4, +5, +6, +7 −1, +1, +3, +5, +7

mass number of most common isotopes (terrestrial abundance, percent) 79 (50.54), 81 (49.46) 127 (100) —

radioactive isotopes (mass numbers) 74–78, 80, 82–90 117–126, 128–139 200−219

heat of fusion (kilocalories per mole) 2.58 3.65 —

heat of vaporization (kilocalories per mole) 7.159 9.889 —

heat of hydration of the −1 ion (kilocalories per mole) 80.3 70.5 —

specific heat (kilocalories per gram per °C at 25 °C)

constant pressure 0.0537 0.034 —

constant volume 0.04257 0.02697 —

critical temperature (°C) 302 512 —

critical pressure (atmospheres) 126 116** —

critical density (grams per cubic cm) 1.064 1.336 —

crystal structure orthorhombic orthorhombic —

electrical resistivity (microhm-cm) 6.5(10¹⁰) (25 °C) 5.85 (25 °C) —

magnetic susceptibility (cubic cm per gram)

gas −73.5(10⁻⁶) −3.9(10⁻⁷) (118 °C) —

liquid −56.4(10⁻⁶) −88.7(10⁻⁶) (solid 28 °C) —

radius

ionic (angstroms) 1.96 2.20 ~2.27

covalent (angstroms) 1.14 1.33 ~1.4

bond energy (kilocalories per mole) 46.1 36.1 —

ionization energy (kilocalories per mole) 273 241 —

electron affinity (kilocalories per mole) 77.5 70.6 —

electronegativity (Allred-Rochow) 2.74 2.21 1.96

*Variation of isotopic abundance in terrestrial samples limits the precision of the atomic weight given.

**Estimated.