SULFUR

CHALCOGENS ELEMENT

Atomic number:	16
Group numbers:	16
Period:	3
Electronic configuration:	[Ne] 3s² 3p⁴
Formal oxidation number:	-2 +4 +6
Electronegativities:	2.58
Atomic radius / pm:	103.5
Relative atomic mass:	[32.059, 32.076]

Sulfur has been known since ancient times. The origin of the name comes from the Sanskrit word sulvere meaning sulfur; also from the Latin word sulphurium meaning sulfur. It is a pale yellow, odourless, brittle solid, which is insoluble in water but soluble in carbon disulfide. Sulfur is found in pure form and in ores like cinnabar, galena, sphalerite and stibnite. Pure form is obtained from underground deposits by the Frasch process. Sulfur is used in matches, gunpowder, medicines, rubber and pesticides, dyes and insecticides, and for making sulfuric acid (H2SO4). The price of 99.5 % pure sulfur powder is 23.60 € for 500 g.

PHYSICAL PROPERTIES
Density / g dm^-3:	2070	(alpha, 293 K)
	1957	(beta, 293 K)
	1891	(liquid, 393 K)
Molar volume / cm³mol^-1:	15.49	(alpha, 293 K)
	16.38	(beta, 293 K)
	16.96	(liquid, 393 K)
Electrical resistivity / µΩcm:	2E+23	(20 °C)

THERMAL PROPERTIES
Thermal conductivity / W m^-1K^-1:	0.269
Melting point / °C:	115.21
Boiling point / °C:	444.60
Heat of fusion / kJ mol^-1:	1.7175
Heat of vaporization / kJ mol^-1:	9.62
Heat of atomization / kJ mol^-1:	276.6

IONIZATION ENERGIES
First ionization energy / kJ mol^-1:	999.60
Second ionization energy / kJ mol^-1:	2251.78
Third ionization energy / kJ mol^-1:	3356.75

ABUNDANCE OF ELEMENT
in the atmosphere / ppm:	1
in the Earth's crust / ppm:	260
in the oceans / ppm:	900

CRYSTALLOGRAPHIC DATA
Crystal structure:	face-centered orthorhombic
Unit-cell dimensions / pm:	a=1046.46, b=1286.60, c=2448.60
Space group:	Fddd

ISOTOPES
Isotope	Relative atomic mass	Mass percent (%)
³²S	31.9720707(1)	95.02(9)
³³S	32.9714585(1)	0.75(4)
³⁴S	33.9678668(1)	4.21(8)
³⁶S	35.9670809(3)	0.02(1)

REDUCTION POTENTIALS
Balanced half-reaction	E^o / V
S(s) + 2e^- → S^2-	- 0.476
S(s) + H⁺ + 2e^- → HS^-	- 0.065
S(s) + 2H⁺ + 2e^- → H₂S(g)	+0.141
SO₄^2- + 4H⁺ + 2e^- → H₂SO₃ + H₂O	+0.172
SO₄^2- + 4H₂O + 2e^- → SO₃^- + 2OH^-	- 0.93
SO₄^2- + 8H⁺ + 6e^- → S(s) + 4H₂O	+0.357
HSO₄^- + 7H⁺ + 6e^- → S(s) + 4H₂O	+0.339
SO₄^2- + 8H⁺ + 8e^- → S^2- + 4H₂O	+0.149
SO₄^2- + 9H⁺ + 8e^- → HS^- + 4H₂O	+0.252
SO₄^2- + 10H⁺ + 8e^- → H₂S(g) + 4H₂O	+0.303
HSO₄^- + 9H⁺ + 8e^- → H₂S(g) + 4H₂O	+0.289
S₂O₈^2- + 2e^- → 2SO₄^2-	+2.01
S₂O₈^2- + 2H⁺ + 2e^- → 2HSO₄^-	+2.123
S₄O₆^2- + 2e^- → 2S₂O₃^2-	+0.08
S₄O₆^2- + 12H⁺ + 10e^- → 4S(s) + 6H₂O	+0.416
S₂O₆^2- + 2e^- → 2SO₃^2-	+0.026
SO₂(g) + 4H⁺ + 4e^- → S(s) + 2H₂O	+0.451
H₂SO₃ + 4H⁺ + 4e^- → S(s) + 3H₂O	+0.450
2SO₃^2- + 6H⁺ + 4e^- → S₂O₃^2- + 3H₂O	+0.705
2HSO₃^- + 4H⁺ + 4e^- → S₂O₃^2- + 3H₂O	+0.491
4HSO₃^- + 8H⁺ + 6e^- → S₄O₆^2- + 6H₂O	+0.581
4H₂SO₃ + 4H⁺ + 6e^- → S₄O₆^2- + 6H₂O	+0.509
SO₃^2- + 6H⁺ + 6e^- → S^2- + 3H₂O	+0.231
S₂^2- + 2H⁺ + 2e^- → 2HS^-	+0.298
S₂^2- + 2e^- → 2S^2-	- 0.524
S₃^2- + 3H⁺ + 4e^- → 3HS^-	+0.097
S₄^2- + 4H⁺ + 6e^- → 4HS^-	+0.033
S₅^2- + 5H⁺ + 8e^- → 5HS^-	+0.003