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lithium (Li)


lithium
A sample of lithium freshly cut
A soft, silvery, reactive metallic element. Lithium is the lightest of all metals and the least reactive of the alkali metals, which occur in group I of the periodic table.


Discovery

Lithium was discovered by Johan A. Arfvedson in Stockholm in 1817. It was first isolated by W. T. Brande and Humphrey Davy in the 19th century, but was not commercially produced until 1923. Its name comes from the Greek lithos for "stone."


Sources of lithium

Some lithium is recovered from the mineral spodumene. Commercial quantities of spodumene are found in a special igneous rock deposit known as pegmatite. In pegmatites, the liquid rock (magma) cools so slowly that crystals have time to grow very large. The largest spodumene crystal ever found was found in a pegmatite in South Dakota.

Most lithium is recovered from brine, or water with a high concentration of lithium carbonate. Brines trapped in the Earth's crust (called subsurface brines) are the major source material for lithium carbonate. These sources are less expensive to mine than from rock such as spodumene, petalite, and other lithium-bearing minerals.

Lithium is made by electrolysis of fused lithium choride.


Uses of lithium

Lithium is used as a heat-transfer medium, because of its high specific heat, and in various alloys, ceramics, and optical forms of glass. Its two stable isotopes are the rarer 6Li, with three protons and three neutrons, and the more common 7Li, with three protons and four neutrons. 6Li is important in thermonuclear processes. Lithium stearate is an additive to lubricating greases.


Lithium in a cosmic context

Some lithium was formed in the immediate aftermath of the Big Bang, along with huge amounts of hydrogen and helium.


atomic number 3
relative atomic mass 6.941
electron configuration 1s22s1
atomic radius 152 pm
relative density 0.534 (at 20°C)
melting point 180.5°C (357.0°F)
boiling point 1,342°C (2,448°F)


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