Gallium is a soft, silvery post-transition metal that melts just above room temperature (≈30 °C). It wets many surfaces and can embrittle other metals but is relatively low in toxicity.
Ground-state configuration: \([Ar]3d^{10}\,4s^2\,4p^1\). Gallium most commonly shows +3 (Ga3+) in salts/oxides and occasionally +1 (Ga+) in some organometallic or subvalent compounds. The filled \(3d^{10}\) subshell influences bonding and size (so-called d-block contraction).
Metallic Ga forms atypical bonding with partial Ga–Ga pairing and a complex structure, weakening metallic cohesion and lowering melting point (~29.8 °C). However, strong covalent/metallic interactions persist in the liquid/atomic phases, giving a high boiling point (~2400 °C) and wide liquid range.
Yes—gallium expands on freezing (opposite most metals). It also wets and can creep into microcracks of glass/porous materials. Store in PTFE or compatible plastic containers, not in aluminum (see below) and avoid tight glassware that could be stressed by expansion.
Liquid or finely divided Ga disrupts Al’s protective oxide and diffuses along grain boundaries, forming brittle intermetallics/solutions. This destroys Al’s mechanical integrity. Keep Ga away from aluminum alloys used in structures.
Yes. Ga(OH)3 dissolves both in acids and bases:
On heating in air, Ga(OH)3 dehydrates to gallium(III) oxide, Ga2O3.
GaAs (gallium arsenide) is a direct-band-gap semiconductor used in high-speed electronics, lasers, and IR devices. GaN (gallium nitride) has a wide band gap (\(E_g\sim 3.4\,\text{eV}\)) enabling blue/UV LEDs, high-power/high-frequency transistors, and efficient solid-state lighting.
Galinstan is a low-melting alloy (Ga–In–Sn) liquid well below 0 °C. It is a non-mercury alternative for thermometers, heat transfer, and soft robotics. Like Ga, it wets surfaces strongly; surface oxidation can be leveraged to shape droplets but also complicates handling.
Ga does not form major ores; it is recovered as a by-product from bauxite (alumina refineries) and zinc processing, concentrated from solutions and purified by solvent extraction, electrolysis, or zone refining for semiconductor-grade material.
Yes. Ga-68 (from a Ge-68/Ga-68 generator) is used in PET imaging with peptides (e.g., DOTATATE). Ga-67 has been used in SPECT for infection/inflammation/oncology imaging. These require licensed facilities and strict radiological safety.
With non-oxidizing acids (oxide removed):
\(\mathrm{2\,Ga + 6\,HCl \rightarrow 2\,GaCl_3 + 3\,H_2}\)
In base (amphoteric dissolution):
\(\mathrm{Ga + 4\,OH^- + 3\,H_2O \rightarrow [Ga(OH)_4]^- + \tfrac{3}{2}H_2}\)
Oxidizing acids (e.g., hot HNO3) passivate/oxidize to Ga2O3 or Ga3+ species.
Metallic Ga is considered low toxicity, but avoid ingestion and prolonged skin contact. Some Ga compounds (e.g., GaCl3) are corrosive/irritant. Use gloves, keep away from aluminum, and clean spills promptly (it will stain/wet many surfaces). Dispose according to local regulations.