Post-transition metalElement 31 · p-block

Gallium (Ga)

Gallium (Ga) is a post-transition metal with atomic number 31 and a standard atomic weight of 69.723. At room temperature it is a solid that melts at 30 °C and boils at 2,229 °C.

31GaGallium69.723

Atomic number

protons

Atomic weight

69.723

CIAAW 2024

Melting point

30 °C

302.91 K

Boiling point

2,229 °C

2,502.15 K

Density

5.91 g/cm³

near room temperature

Electronegativity

1.81

Pauling scale

State at 25 °C

Solid

Discovered

1875

France

Gallium at a glance

Identity

Symbol	Ga
Atomic number (Z)	31
Atomic weight	69.723 ± 0.001 (CIAAW 2024)
Category	Post-transition metal
Group	13 — boron group
Period	4
Block	p-block
CAS number	7440-55-3

Atomic properties

Electron configuration	[Ar] 3d¹⁰ 4s² 4p¹ Full: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p¹
Electrons per shell	2, 8, 18, 3
Oxidation states	+3 Less common: -5, -4, -3, -2, -1, 0, +1, +2
Electronegativity (Pauling)	1.81
First ionisation energy	5.999 eV (578.8 kJ/mol) 2nd: 20.515 eV · 3rd: 30.726 eV
Electron affinity	0.43 eV
Atomic radius (empirical)	130 pm
Covalent radius	124 pm
Van der Waals radius	187 pm

Physical properties

State at 25 °C	Solid
Melting point	29.76 °C · 85.6 °F · 302.91 K
Boiling point	2,229 °C · 4,044.2 °F · 2,502.15 K
Density	5.91 g/cm³
Specific heat capacity	0.373 J/(g·K)
Thermal conductivity	28.1 W/(m·K)
Crystal structure	Orthorhombic

Isotopes & abundance

Natural occurrence	Primordial
Radioactive	No
Natural isotopes (abundance)	⁶⁹Ga 60.108%, ⁷¹Ga 39.892%
Stable isotopes	7
Known isotopes	33
Abundance in Earth's crust	19 mg/kg
Abundance in seawater	0.00003 mg/L

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

Gallium electron configuration

Gallium has 31 electrons. Written in short form, its ground-state configuration is [Ar] 3d¹⁰ 4s² 4p¹ — the electrons of the noble gas argon, plus 3d¹⁰ 4s² 4p¹.Written out in full: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p¹.

As a member of group 13 it has 3 valence electrons in its outer shell (shell 4), which largely decide its chemistry.

3d↑↓↑↓↑↓↑↓↑↓

4s↑↓

4p↑

Discovery and name

Discovered

1875 — Paul-Émile Lecoq de Boisbaudran · France.

Name

Latin Gallia, France.

Known for

Melts at 29.8 °C — in your hand. Gallium arsenide and gallium nitride are semiconductors for LEDs, lasers, 5G and fast chargers.

Isotopes of gallium

Naturally occurring gallium is a mix of 2 isotopes. Each has 31 protons; they differ in the number of neutrons:

Isotope	Protons	Neutrons	Natural abundance	Stability
⁶⁹Ga	31	38	60.108%	stable
⁷¹Ga	31	40	39.892%	stable

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

Gallium compared with group 13

The other elements in group 13 (boron group), from top to bottom of the table:

Element	Z	Atomic weight	Melting point	Boiling point	Density	Electronegativity
Boron	5	10.81	2,077 °C	4,000 °C	2.34 g/cm³	2.04
Aluminum	13	26.982	660 °C	2,519 °C	2.7 g/cm³	1.61
Gallium	31	69.723	30 °C	2,229 °C	5.91 g/cm³	1.81
Indium	49	114.82	157 °C	2,027 °C	7.31 g/cm³	1.78
Thallium	81	204.38	304 °C	1,473 °C	11.8 g/cm³	1.62
Nihonium	113	[286]	—	—	16 g/cm³ (pred.)	—

Frequently asked questions

6 answers

What is the atomic mass of gallium?

The standard atomic weight of gallium is 69.723 ± 0.001 (CIAAW 2024), so one mole weighs about 69.723 grams.

How many protons, neutrons and electrons does gallium have?

A neutral gallium atom has 31 protons and 31 electrons. Its most common isotope, gallium-69, has 38 neutrons.

What is the electron configuration of gallium?

[Ar] 3d¹⁰ 4s² 4p¹ (in full: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p¹).

What are the melting and boiling points of gallium?

Gallium melts at 29.76 °C (85.6 °F) and boils at 2,229 °C (4,044.2 °F).

Is gallium a metal?

Gallium is a metal. It is in group 13, period 4, and is a solid at room temperature.

Who discovered gallium?

1875 — Paul-Émile Lecoq de Boisbaudran (France).