16
S
32.06
Sulfur
General | States | Energies
Oxidation & Electrons | Appearance & Characteristics
Reactions | Compounds | Radius | Conductivity
Abundance & Isotopes

Sulfur
Deposits of sulfur around a volcanic vent.




General:

Name: Sulfur Symbol: S
Type: Non-Metal, Chalcogen Atomic weight: 32.06
Density @ 293 K: 2.07 g/cm3 Atomic volume: 15.5 cm3/mol
Discovered: Sulfur has been known since ancient times and is referred to in the Bible as brimstone. The name may have been derived from the Arabic 'sufra', meaning yellow.

States

State (s, l, g): solid
Melting point: 388.4 K   (115.2 oC) Boiling point: 717.9 K   (444.7 oC)

Energies

Specific heat capacity: 0.71 J g-1 K-1 Heat of atomization: 279 kJ mol-1
Heat of fusion: 1.7175 kJ mol-1 Heat of vaporization: 9.8 kJ mol-1 of S2
1st ionization energy: 999.6 kJ mol-1 2nd ionization energy: 2251 kJ mol-1
3rd ionization energy: 3360.6 kJ mol-1 Electron affinity: 200.4144 kJ mol-1

Oxidation & Electrons

Shells: 2,8,6 Electron configuration: [Ne] 3s2 3p4
Minimum oxidation number: -2 Maximum oxidation number: 6
Min. common oxidation no.: -2 Max. common oxidation no.: 6
Electronegativity (Pauling Scale): 2.58 Polarizability volume: 2.9 Å3

Appearance & Characteristics

Structure: S8 rings
sulfur 8
Color: yellow
Hardness: 2 mohs

Sulfur reacts very vigorously with zinc. Here's a test firing of a sulfur/zinc rocket.

Crystallization of liquid sulfur.
Harmful effects:
Elemental sulfur is considered to be of low toxicity. Compounds such as carbon disulfide, hydrogen sulfide, and sulfur dioxide are toxic. For example, at 0.03 parts per million, we can smell hydrogen sulfide but it is regarded as safe for eight hours of exposure. At 4 ppm it may cause eye irritatation. At 20 ppm exposure for more than a minute causes severe injury to eye nerves. At 700 ppm breathing stops. Death will result if there is not a quick rescue. Permanent brain damage may result. (1)

Characteristics:
Sulfur is a soft, pale yellow, odorless, brittle solid. It is insoluble in water, but soluble in carbon disulfide. It burns with a blue flame, oxidizing to sulfur dioxide.

Sulfur exists in several crystalline and amorphous allotropes. The most common form is yellow, orthorhombic alpha-sulfur, which contains puckered rings of S8.

Sulfur is multivalent and combines, with valence 2, 4, or 6, with almost all other elements. The best known sulfur compound is hydrogen sulfide (H2S). This is a toxic gas that smells like rotten eggs; the smell is used in stink bombs, many of which release a small amount of hydrogen sulfide.

Uses:
Sulfur's main commercial use is as a reactant in the production of sulfuric acid (H2SO4). Sulfuric acid is the industrialized world's number one bulk chemical, required in large quantities in lead-acid batteries for automotive use.

Sulfur is also used in the vulcanization of natural rubber, as a fungicide, in black gunpowder, in detergents and in the manufacture of phosphate fertilizers.

Sulfur is a vital element for all forms of life. It is a component of two amino acids, cysteine and methionine.

Reactions

Reaction with air: vigorous, w/ht ⇒ SO2 Reaction with 6 M HCl: none
Reaction with 15 M HNO3: vigorous, ⇒ H2SO4, NOx Reaction with 6 M NaOH: none

Compounds

Oxide(s): SO2, SO3 Chloride(s): S2Cl2, SCl2
Hydride(s): H2S (hydrogen sulfide)

Radius

Atomic radius: 100 pm Ionic radius (1+ ion): pm
Ionic radius (2+ ion): pm Ionic radius (3+ ion): pm
Ionic radius (2- ion): 170 pm Ionic radius (1- ion): pm

Conductivity

Thermal conductivity: 0.205 W m-1 K-1 Electrical conductivity: 5.0 x 10-14 S cm-1

Abundance & Isotopes

Abundance earth's crust: 350 parts per million by weight, 225 parts per million by moles
Abundance solar system: 400 parts per million by weight, 10 parts per million by moles
Cost, pure: $50 per 100g
Cost, bulk: $ per 100g
Source: Sulfur deposits are found naturally in areas around hot springs and in volcanic regions. It is also widely found in nature as iron pyrites (iron sulfide), galena (lead sulfide), gypsum (calcium sulfate), Epsom salts (magnesium sulfate) and many other minerals. Sulfur is recovered commercially from underground deposits using the Frasch Process - superheated water and steam are pumped underground, where they melt the sulfur, allowing it to be pumped to the surface. Sulfur is also obtained commercially as a by-product of refining crude oil.
Isotopes: Sulfur has 18 isotopes whose half-lives are known, with mass numbers 27 to 45. Of these, four are stable: 32S, 33S, 34S, and 36S. 95% of naturally occurring sulfur is in the form of 32S.

References

1. Toxicity of hydrogen sulfide gas.