Gallium

This article is about the chemical element. For other uses, see Gallium (disambiguation).

Gallium, ₃₁Ga

Gallium
Pronunciation	/ˈɡæliəm/ ⓘ ​(GAL-ee-əm)
Appearance	silvery blue
Standard atomic weight Ar°(Ga)
	69.723±0.001 69.723±0.001 (abridged)
Gallium in the periodic table
Hydrogen Helium Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson Al ↑ Ga ↓ In zinc ← gallium → germanium
Atomic number (Z)	31
Group	group 13 (boron group)
Period	period 4
Block	p-block
Electron configuration	[Ar] 3d10 4s2 4p1
Electrons per shell	2, 8, 18, 3
Physical properties
Phase at STP	solid
Melting point	302.9146 K ​(29.7646 °C, ​85.5763 °F)
Boiling point	2676 K ​(2403 °C, ​4357 °F)
Density (at 20° C)	5.907 g/cm3
when liquid (at m.p.)	6.095 g/cm3
Heat of fusion	5.59 kJ/mol
Heat of vaporization	256 kJ/mol
Molar heat capacity	25.86 J/(mol·K)
Specific heat capacity	370.896 J/(kg·K)
Vapor pressure P (Pa) 1 10 100 1 k 10 k 100 k at T (K) 1310 1448 1620 1838 2125 2518
Atomic properties
Oxidation states	common: +3 −5, −4, −3, −2, −1, 0, +1, +2
Electronegativity	Pauling scale: 1.81
Ionization energies	1st: 578.8 kJ/mol 2nd: 1979.3 kJ/mol 3rd: 2963 kJ/mol (more)
Atomic radius	empirical: 135 pm
Covalent radius	122±3 pm
Van der Waals radius	187 pm
Spectral lines of gallium
Other properties
Natural occurrence	primordial
Crystal structure	​base-centered orthorhombic (oS8)
Lattice constants	a = 452.05 pm b = 766.25 pm c = 452.66 pm (at 20 °C)
Thermal expansion	20.5×10−6/K (at 20 °C)
Thermal conductivity	40.6 W/(m⋅K)
Electrical resistivity	270 nΩ⋅m (at 20 °C)
Magnetic ordering	diamagnetic
Molar magnetic susceptibility	−21.6×10−6 cm3/mol (at 290 K)
Young's modulus	9.8 GPa
Speed of sound thin rod	2740 m/s (at 20 °C)
Poisson ratio	0.47
Mohs hardness	1.5
Brinell hardness	56.8–68.7 MPa
CAS Number	7440-55-3
History
Naming	after Gallia (Latin for: France), homeland of the discoverer
Prediction	Dmitri Mendeleev (1871)
Discovery and first isolation	Lecoq de Boisbaudran (1875)
Isotopes of gallium
Main isotopes Decay Isotope abun­dance half-life (t1/2) mode pro­duct 66Ga synth 9.304 h β+ 66Zn 67Ga synth 3.2617 d ε 67Zn 68Ga synth 67.84 min β+ 68Zn 69Ga 60.1% stable 70Ga synth 21.14 min β− 70Ge ε 70Zn 71Ga 39.9% stable 72Ga synth 14.025 h β− 72Ge 73Ga synth 4.86 h β− 73Ge

Gallium is a chemical element; it has symbol Ga and atomic number 31. Discovered by the French chemist Paul-Émile Lecoq de Boisbaudran in Paris, France, 1875, elemental gallium is a soft, silvery metal at standard temperature and pressure with a complex orthorhombic crystal structure. In its liquid state, it becomes silvery white. If enough force is applied, solid gallium may fracture conchoidally. Gallium does not occur as a free element in nature, but rather as gallium(III) compounds in trace amounts in zinc ores (such as sphalerite) and in bauxite.

The melting point of gallium, 29.7646 °C (85.5763 °F; 302.9146 K), is used as a temperature reference point. One of only four metal elements that is liquid at, or near, normal room temperature, gallium will melt in a person's hands at normal human body temperature of 37 °C (99 °F). Gallium alloys with low temperatures are used in thermometers as a non-toxic and environmentally friendly alternative to mercury, and can withstand higher temperatures than mercury. A melting point of −19 °C (−2 °F), well below the freezing point of water, is claimed for the alloy galinstan (62–⁠95% gallium, 5–⁠22% indium, and 0–⁠16% tin by weight), but that may be the freezing point with the effect of supercooling.

Gallium is predominantly used in electronics. Gallium arsenide, the primary chemical compound of gallium in electronics, is used in microwave circuits, high-speed switching circuits, and infrared circuits. Semiconducting gallium nitride and indium gallium nitride produce blue and violet light-emitting diodes and diode lasers. Gallium is also used in the production of artificial gadolinium gallium garnet for jewelry. It has no known natural role in biology. Gallium(III) behaves in a similar manner to ferric salts in biological systems and has been used in some medical applications, including pharmaceuticals and radiopharmaceuticals.