Gallium

Gallium (chemical symbol: Ga) is element 31 on the periodic table. It is a soft, gray metal that is rare on Earth. It can easily be melted just by holding it in your hand, as its melting point is very low 29.76 Celsius (85.58 Fahrenheit), however it also sticks to your hand a lot, unlike Mercury. Gallium is a semiconductor, and as the compound Gallium arsenide it is used in electronics and LEDs. Then, Gallium is also used in mirrors. Gallium can also be alloyed with Indium and Tin to create Galinstan. Gallium is similar to the elements Aluminium, Indium and Mercury.

Gallium, ₃₁Ga

Gallium
Pronunciation	/ˈɡæliəm/ ​(GAL-ee-əm)
Appearance	silvery blue
Standard atomic weight Ar°(Ga)
	69.723(1)
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	2673 K ​(2400 °C, ​4352 °F)
Density (near r.t.)	5.91 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)
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	−5, −4, −3, −2, −1, 0, +1, +2, +3 (an amphoteric oxide)
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	​orthorhombic
Speed of sound thin rod	2740 m/s (at 20 °C)
Thermal expansion	18 µm/(m⋅K) (at 25 °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
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 abun­dance half-life (t1/2) mode pro­duct 66Ga synth 9.5 h β+ 66Zn 67Ga synth 3.3 d ε 67Zn 68Ga synth 1.2 h β+ 68Zn 69Ga 60.1% stable 70Ga synth 21 min β− 70Ge ε 70Zn 71Ga 39.9% stable 72Ga synth 14.1 h β− 72Ge 73Ga synth 4.9 h β− 73Ge

Crystals of gallium joined together

Gallium's existence was predicted by Dmitri Mendeleev in 1871. Four years later, it was discovered by Paul-Émile Lecoq de Boisbaudran.