Antimony is a metalloid, which means it shows properties of both metals and nonmetals.

How many protons does antimony have?

Antimony has 51 protons. Its atomic number is 51, which is also the number of electrons in a neutral atom of antimony.

What group and period is antimony in?

Antimony is in group 15 and period 5 of the periodic table, in the p-block.

What is the atomic mass of antimony?

The atomic mass of antimony is 121.76 u (unified atomic mass units).

Element 51

Antimony (Sb)

Metalloid · Period 5 · Group 15 · p-block

Antimony (Sb) is element 51 of the periodic table, a metalloid in period 5, group 15 (p-block) with an atomic mass of 121.76 and is a solid at standard conditions.

At a glance

Atomic number: 51
Symbol: Sb
Atomic mass: 121.76 u
Category: Metalloids
Period: 5
Group: 15
Block: p-block
Phase at STP: solid

Electron structure

Electron configuration: 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p3
Shorthand configuration: [Kr] 4d10 5s2 5p3
Electrons per shell: 2, 8, 18, 18, 5
Oxidation states: -3, -2, -1, +1, +2, +3, +4, +5

Physical properties

Melting point: 903.78 K (630.63 °C)
Boiling point: 1,860 K (1,586.85 °C)
Density: 6.685 g/cm³
Phase: solid

Atomic properties

Electronegativity (Pauling): 2.05
Atomic radius: 133 pm
Covalent radius: 139 pm
Van der Waals radius: 206 pm
First ionization energy: 834 kJ/mol
Electron affinity: 103 kJ/mol

Notable isotopes

Notable isotopes of Antimony: mass number, atomic mass, natural abundance, and stability.
Isotope	Mass	Abundance	Stability
Sb-121	120.90381	57.21%	Stable

Common uses

Flame retardants
Batteries
Alloys
Semiconductors

Discovery

Discovered by: Known since antiquity
Country: Unknown

Frequently asked questions

Is antimony a metal?: Antimony is a metalloid, which means it shows properties of both metals and nonmetals.
How many protons does antimony have?: Antimony has 51 protons. Its atomic number is 51, which is also the number of electrons in a neutral atom of antimony.
What group and period is antimony in?: Antimony is in group 15 and period 5 of the periodic table, in the p-block.
What is the atomic mass of antimony?: The atomic mass of antimony is 121.76 u (unified atomic mass units).

Keep exploring

Antimony's row is on the printable element property sheet, and its tile is on the periodic table wall chart - the same numbers as above, laid out for A4 or A3 paper.