Reactive nonmetalElement 16 · p-block

Sulfur (S)

Sulfur (S) is a reactive nonmetal with atomic number 16 and a standard atomic weight of 32.06. At room temperature it is a solid that melts at 115 °C and boils at 445 °C.

16SSulfur32.06

Atomic number

protons

Atomic weight

32.06

CIAAW 2024

Melting point

115 °C

388.36 K

Boiling point

445 °C

717.76 K

Density

2.07 g/cm³

near room temperature

Electronegativity

2.58

Pauling scale

State at 25 °C

Solid

Discovered

Prehistoric

Sulfur at a glance

Identity

Symbol	S
Atomic number (Z)	16
Atomic weight	32.06 ± 0.02 (CIAAW 2024)
Category	Reactive nonmetal
Group	16 — chalcogens (oxygen group)
Period	3
Block	p-block
CAS number	7704-34-9

Atomic properties

Electron configuration	[Ne] 3s² 3p⁴ Full: 1s² 2s² 2p⁶ 3s² 3p⁴
Electrons per shell	2, 8, 6
Oxidation states	-2, +2, +4, +6 Less common: -1, 0, +1, +3, +5
Electronegativity (Pauling)	2.58
First ionisation energy	10.36 eV (999.6 kJ/mol) 2nd: 23.338 eV · 3rd: 34.86 eV
Electron affinity	2.077 eV
Atomic radius (empirical)	100 pm
Covalent radius	103 pm
Van der Waals radius	180 pm

Physical properties

State at 25 °C	Solid
Melting point	115.2 °C · 239.4 °F · 388.36 K
Boiling point	444.6 °C · 832.3 °F · 717.76 K
Density	2.07 g/cm³
Specific heat capacity	0.708 J/(g·K)
Thermal conductivity	0.27 W/(m·K)
Crystal structure	Orthorhombic

Isotopes & abundance

Natural occurrence	Primordial
Radioactive	No
Natural isotopes (abundance)	³²S 94.85%, ³⁴S 4.365%, ³³S 0.763%, ³⁶S 0.0158%
Stable isotopes	5
Known isotopes	24
Abundance in Earth's crust	350 mg/kg
Abundance in seawater	905 mg/L

Atomic weights: CIAAW Abridged Standard Atomic Weights 2024. Other properties: standard reference compilations, checked October 2026; predicted values are marked.

Sulfur electron configuration

Sulfur has 16 electrons. Written in short form, its ground-state configuration is [Ne] 3s² 3p⁴ — the electrons of the noble gas neon, plus 3s² 3p⁴.Written out in full: 1s² 2s² 2p⁶ 3s² 3p⁴.

As a member of group 16 it has 6 valence electrons in its outer shell (shell 3), which largely decide its chemistry.

3s↑↓

3p↑↓↑↑

Discovery and name

Discovered

Prehistoric — Known since antiquity (brimstone).

Name

Latin sulfur (sulphurium).

Known for

Known since antiquity as brimstone. Most is turned into sulfuric acid, the most-produced industrial chemical; it also vulcanises rubber.

Isotopes of sulfur

Naturally occurring sulfur is a mix of 4 isotopes. Each has 16 protons; they differ in the number of neutrons:

Isotope	Protons	Neutrons	Natural abundance	Stability
³²S	16	16	94.85%	stable
³⁴S	16	18	4.365%	stable
³³S	16	17	0.763%	stable
³⁶S	16	20	0.0158%	stable

24 isotopes of sulfur are known in our data set (half-lives as published in nuclear data tables).

Sulfur compared with group 16

The other elements in group 16 (chalcogens (oxygen group)), from top to bottom of the table:

Element	Z	Atomic weight	Melting point	Boiling point	Density	Electronegativity
Oxygen	8	15.999	-219 °C	-183 °C	1.429 g/L	3.44
Sulfur	16	32.06	115 °C	445 °C	2.07 g/cm³	2.58
Selenium	34	78.971	221 °C	685 °C	4.809 g/cm³	2.55
Tellurium	52	127.60	450 °C	988 °C	6.232 g/cm³	2.1
Polonium	84	[209]	254 °C	962 °C	9.2 g/cm³	2
Livermorium	116	[293]	—	—	12.9 g/cm³ (pred.)	—

Frequently asked questions

6 answers

What is the atomic mass of sulfur?

The standard atomic weight of sulfur is 32.06 ± 0.02 (CIAAW 2024), so one mole weighs about 32.06 grams.

How many protons, neutrons and electrons does sulfur have?

A neutral sulfur atom has 16 protons and 16 electrons. Its most common isotope, sulfur-32, has 16 neutrons.

What is the electron configuration of sulfur?

[Ne] 3s² 3p⁴ (in full: 1s² 2s² 2p⁶ 3s² 3p⁴).

What are the melting and boiling points of sulfur?

Sulfur melts at 115.21 °C (239.4 °F) and boils at 444.61 °C (832.3 °F).

Is sulfur a metal?

Sulfur is a nonmetal. It is in group 16, period 3, and is a solid at room temperature.

Who discovered sulfur?

Sulfur has been known since ancient times.