Chemical element · reference page

31Ga

Gallium

Gallium is element 31 (Ga), located in period 4, group 13 and the p block. At room temperature its reference phase is solid. Its electron configuration is [Ar] 3d10 4s2 4p1.

Atomic number31

Standard atomic weight69.723(1)

Group13

Period4

Blockp

Electron configuration[Ar] 3d10 4s2 4p1

Electronic structure

What controls its chemistry

Atoms in group 13 have three valence electrons in the outer s and p subshells. The balance between covalent bonding and positive oxidation states changes down the group as atomic size and metallic character increase.

Gallium is therefore best understood by comparing it with the elements immediately above and below it rather than by treating group 13 as chemically uniform.

Chemical forms

Compounds, ions and materials

Group 13 chemistry includes oxides, halides and covalent or ionic compounds in positive oxidation states. The lighter elements show more covalent character, while the heavier members become progressively more metallic.

Physical behaviour

State and phase changes

The reference phase at room temperature is solid. The listed density is 5.91 g/cm³. The melting point is 302.9 K (29.76 °C). The boiling point is 2 673 K (2 400 °C). Pressure, purity and crystal structure can shift measured physical properties.

Occurrence and applications

Where gallium is found and used

In practice, gallium is encountered in semiconductors, lEDs and measurement instruments.

In practice

Examples of real uses

Semiconductors

Compounds or doped forms of gallium are used to control electrical conduction in semiconductor devices.

LEDs

Gallium is used in semiconductor compounds that emit light when charge carriers recombine.

Measurement instruments

Gallium is used in sensors and precision instruments where stable physical, optical or electrical properties are required.

Periodic position

What its neighbours tell us

Gallium is in period 4 and group 13. In the neighbourhood shown here, it lies between zinc and germanium in the same period; aluminium is above it and indium 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

Classificationpost-transition metal

Phase at room temperatureSolid

Electron shells2 · 8 · 18 · 3

Density5.91 g/cm³

Melting point302.9 K (29.76 °C)

Boiling point2 673 K (2 400 °C)

Pauling electronegativity1.81

First ionisation energy578.8 kJ/mol

Electron affinity41 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

The discovery of gallium is associated with Lecoq de Boisbaudran. Recognition of the element, isolation of a pure sample and assignment of its modern atomic number did not necessarily occur at the same time.

Isotopes and atomic weight

How isotope composition changes the numbers

The standard atomic weight is 69.723(1). This value refers to the isotopic composition of natural terrestrial material, not to the mass of one specific atom.

Gallium 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 gallium depend on chemical form, dose and route of exposure. Pure gallium, 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.