Chemical element · reference page

16S

Sulfur

Sulfur is element 16 (S), located in period 3, group 16 and the p block. At room temperature its reference phase is solid. Its electron configuration is [Ne] 3s2 3p4.

Atomic number16

Standard atomic weight[32.059, 32.076]

Group16

Period3

Blockp

Electron configuration[Ne] 3s2 3p4

Electronic structure

What controls its chemistry

Group 16 atoms have six valence electrons. Bonding often involves gaining or sharing two electrons, while the heavier members can access a wider range of oxidation states.

For sulfur, this outer-shell structure helps explain the importance of oxides, sulfides, oxoanions and covalent compounds across the chalcogen family.

Chemical forms

Compounds, ions and materials

Hydrides, oxides, sulfides or selenides, halides and oxoanions are important across group 16. The −2 oxidation state is common for the lighter chalcogens, while positive oxidation states become increasingly accessible in heavier compounds.

Physical behaviour

State and phase changes

The reference phase at room temperature is solid. The listed density is 2.07 g/cm³. The melting point is 388.4 K (115.2 °C). The boiling point is 717.8 K (444.6 °C). Pressure, purity and crystal structure can shift measured physical properties.

Occurrence and applications

Where sulfur is found and used

In practice, sulfur is encountered in fertiliser production, sulfuric acid and rubber vulcanisation.

In practice

Examples of real uses

Fertiliser production

Sulfur is part of fertiliser chemistry or the industrial processes used to supply essential plant nutrients.

Sulfuric acid

Sulfur is the central element in sulfuric acid, one of the highest-volume industrial chemicals.

Rubber vulcanisation

Sulfur forms cross-links between polymer chains, improving the strength and elasticity of rubber.

Periodic position

What its neighbours tell us

Sulfur is in period 3 and group 16. In the neighbourhood shown here, it lies between phosphorus and chlorine in the same period; oxygen is above it and selenium below it in the same group. These positions make it possible to compare atomic size, ionisation energy and bonding behaviour with nearby elements.

Reference data

Physical and atomic properties

Classificationpolyatomic nonmetal

Phase at room temperatureSolid

Electron shells2 · 8 · 6

Density2.07 g/cm³

Melting point388.4 K (115.2 °C)

Boiling point717.8 K (444.6 °C)

Pauling electronegativity2.58

First ionisation energy999.6 kJ/mol

Electron affinity200.4 kJ/mol

Values describe the element or neutral atom where applicable. Physical data can depend on allotrope, pressure and measurement conditions.

History

Discovery and identification

Sulfur or its materials were known in antiquity, long before atomic theory. The modern element is defined by atomic number 16, which distinguishes it unambiguously from compounds and mixtures known to early craftspeople.

Isotopes and atomic weight

How isotope composition changes the numbers

The standard atomic weight is given as the interval [32.059, 32.076]. Natural samples can differ slightly in isotope proportions, so a single universal decimal value would hide real variation between materials.

Sulfur has at least one stable isotope. Different isotopes have the same number of protons and therefore the same element identity, but different neutron numbers and atomic masses.

Safety

Handling and exposure

The hazards associated with sulfur depend on chemical form, dose and route of exposure. Pure sulfur, its ions and its compounds can have very different biological and environmental effects, so safety data should be checked for the actual substance being handled.