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H

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Li

Be

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Na

Mg

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Element Fact
Rhenium was the last naturally occurring element to be identified, in 1925. It was so rare that only 1 g of the metal was extracted out of 660 kg of molybdenite ore.

Lithium, Li

lithium sample

Atomic number: 3
Atomic mass: 6.941(2)
Natural abundance: 18 ppm
Isotopes:
6Li (6.0151223) - 7.5%
7Li (7.016004) - 92.5%

History and Production

Derived from the Greek word lithos, meaning stone. Discovered in 1817 by J. A. Arfvedson from the mineral petalite, LiAlSi4O10. The metal can be produced electolytically from the fused lithium chloride. It is used to produce high-strength, low-density aluminium alloys for aircraft construction. The chloride compound, LiCl is used a brazing flux for the Al automobile parts. Lithium stearate is used as a high temperature lubricant.

Physical Data

Silvery in appearance, it is the lightest of all metals, with a density only about half that of water. Since it is very reactive with the water and the moisture in air, it is usually kept in oil. It produces a crimson color to a flame, but appears dazzling white when burns strongly. It does not occur free in nature, but found in igneous rocks and mineral springs and consists of 18 ppm by weight in crustal rocks. Some important commercial minerals are spodumene, LiAlSi2O6 and petalite.

Interatomic distance: 304 pm
Melting point: 180.5C
Boiling point: 1342C
Thermal conductivity/Wm-1K-1: 84.7 (27C)
Density/kgm-3: 534 (20C), 515 (m.p.)

Standard Thermodynamic Data (atomic gas)

Enthalpy of formation: 159.3 kJ/mol
Gibbs free energy of formation: 126.6 kJ/mol
Entropy: 138.8 J/mol K
Heat capacity: 20.8 J/mol K

Electronic data

Electronic configuration: [He] 2s1
Term symbol: 2S1/2
Electron affinity: 59.6327 kJ/mol   Electronegativity (Pauline): 0.98
Ionization energy (first, second, third): 513.3, 7298.0, 11814.8 kJ/mol

Chemical properties

The chemical behavior of lithium, in many respect, is quite similar to magnesium, an alikaline earth metal. This is due to its unusually small Li+ ion. For instance, lithium can react with nitrogen to form nitride, Li3N while sodium and potassium do not. Lithium only reacts smoothly with water whereas sodium and potassium acts vigorously with water.


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