Sulfur at a glance
- Atomic number
- 16
- Symbol
- S
- Atomic mass
- 32.06 u
- Category
- Reactive nonmetal
- Group / period
- 16 / 3
- Electron configuration
- [Ne] 3s 2 3p 4
- State at 25 °C
- Solid
- Melting point
- 115.2 °C
- Boiling point
- 444.6 °C
- Density
- 2.067 g/cm³
- Electronegativity
- 2.58
- 1st ionization energy
- 1000 kJ/mol
- Oxidation states
- −2, +4, +6
- Discovered
- Antiquity
Atomic structure
A neutral sulfur atom has 16 protons and 16 electrons, and its most common isotope carries about 16 neutrons. One atom weighs about 5.32 × 10⁻²⁶ kg, so a mole of sulfur (6.022 × 10²³ atoms) weighs 32.06 g. That nucleus holds 1 neutrons for every proton, close to the one-to-one balance that light nuclei prefer. The electrons fill 3 shells (K 2, L 8, M 6), which gives the configuration [Ne] 3s 2 3p 4. With 6 electrons in its outer shell, it tends to gain or share electrons to complete its outer shell. It has 4 stable isotopes: S-32, S-33, S-34 and S-36. No other element has a stable isotope with mass number 32, so S-32 has no stable isobars; its neighbours on that line decay into it or away from it.
Physical properties
At room temperature (25 °C) sulfur is a solid. It melts at 115.2 °C and boils at 444.6 °C, so it stays liquid across a 329.4-degree range. It stays solid in boiling water but would melt in a hot kitchen oven. Its density is 2.067 g/cm³, 2.07 times as dense as water. Its atoms have a radius of about 100 pm (Phosphorus next door is 100 pm). In the solid, its atoms pack into an orthorhombic lattice.
Chemical behaviour
Its electronegativity is 2.58 on the Pauling scale. Pulling off its outermost electron takes 1000 kJ/mol, less than Oxygen above it (1314 kJ/mol). A bond between sulfur and chlorine would be polar covalent, with an electronegativity difference of 0.58. It releases 200 kJ/mol when it gains an extra electron. Its common oxidation states are −2, +4, +6, so in compounds you will usually meet it as S²⁻, S⁴⁺ and S⁶⁺. Group 16 also holds Oxygen, Selenium, Tellurium, Polonium and Livermorium, which share its outer-shell pattern. Its Lewis symbol is S surrounded by 6 dots. Handle with care: as a pure element it is flammable or reacts with water.
Where it comes from
It makes up 350 mg/kg of Earth's crust, the 16th most abundant element there. In the human body it accounts for about 0.3 % of body mass. It has been known since ancient times, one of only 11 elements people used before modern chemistry.