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

General properties
Pronunciation	/ˈɡæliəm/ ​(GAL-ee-əm)
Appearance	silvery blue
Standard atomic weight (Ar, standard)	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 n/a
Period	period {{{period}}}
Block	[[{{{block}}}-block]]
Electron configuration	[Ar] 3d10 4s2 4p1
Electrons per shell	2, 8, 18, 3
Physical properties
Phase at STP	Ga: 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, −2, −1, +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	Ga: 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
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)
Iso­tope Abun­dance Half-life (t1/2) Decay mode Pro­duct

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.

Gallium Media

• 

  Crystallization of gallium from the melt

• 

  Liquid gallium at 86 °F (30 °C)

• Small gallium droplets fusing together

• 

  99.9999% (6N) gallium sealed in vacuum ampoule

• 

  Bauxite mine in Jamaica (1984)

• 

  Blue LED Christmas lamps and reflection on wall

• 

  Owing to their low melting points, gallium and its alloys can be shaped into various 3D forms using 3D printing and additive manufacturing.