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Lithium

From Academic Kids

lithiumberyllium
H
Li
Na  
 
 
General
Name, Symbol, Number Lithium, Li, 3
Series Alkali metal
Group, Period, Block 1(IA), 2, s
Density, Hardness 535 kg/m3, 0.6
Appearance silvery white/grey
Atomic properties
Atomic weight 6.941 amu
Atomic radius (calc.) 145 (167) pm
Covalent radius 134 pm
van der Waals radius 182 pm
Electron configuration [He]2s1
e- 's per energy level 2, 1
Oxidation states (Oxide) 1 (strong base)
Crystal structure Cubic body centered
Physical properties
State of matter solid (nonmagnetic)
Melting point 453.69 K (356.97 ?F)
Boiling point 1615 K (2448 ?F)
Molar volume 13.02 ×10-6 m3/mol
Heat of vaporization 145.92 kJ/mol
Heat of fusion 3 kJ/mol
Vapor pressure 163 µPa (453.7 K)
Speed of sound 6000 m/s (25 °C)
Miscellaneous
Electronegativity 0.98 (Pauling scale)
Specific heat capacity 3582 J/(kg·K)
Electrical conductivity 10.8 MS/m
Thermal conductivity 84.7 W/(m·K)
1st ionization potential 520.2 kJ/mol
2nd ionization potential 7298.1 kJ/mol
3rd ionization potential 11815.0 kJ/mol
Most stable isotopes
iso NA half-life DM DE (MeV) DP
6Li 7.5%* Stable with 3 neutrons
7Li 92.5%* Stable with 4 neutrons
*Lithium-6 content may be as low as 3.75% in natural samples.
Lithium-7 would therefore have a content of up to 96.25%.
SI units & STP are used except where noted.

Lithium is the chemical element with symbol Li and atomic number 3. In the periodic table, it is located in group 1, among the alkali metals. Lithium in its pure form is a soft, silver white metal, that tarnishes and oxidizes very rapidly in air and water. It is the lightest solid element and is primarily used in heat transfer alloys, in batteries and serves as a component in some drugs known as mood stabilizers.

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Contents

Notable characteristics

Lithium is the lightest metal and has a density that is only half that of water. Like all alkali metals, lithium reacts easily in water and does not occur freely in nature due to its activity, nevertheless it is still less reactive than the chemically similar sodium. When placed over a flame, this metal gives off a striking crimson color but when it burns strongly, the flame becomes a brilliant white. Lithium is a univalent element.

Applications

Because of its large specific heat (the largest of any solid), lithium is used in heat transfer applications. It is also an important battery anode material due to its high electrochemical potential. Other uses:

History

Lithium (Greek lithos, meaning "stone") was discovered by Johann Arfvedson in 1817. Arfvedson found the new element within the minerals spodumene and lepidolite in a petalite ore, LiAl(Si2O5)2, he was analyzing from the island [[Ut?weden|Ut?in Sweden. In 1818 Christian Gmelin was the first to observe that lithium salts give a bright red color in flame. Both men tried and failed to isolate the element from its salts, however.

The element was not isolated until William Thomas Brande and Sir Humphrey Davy later used electrolysis on lithium oxide. Commercial production of lithium metal was achieved in 1923 by the German company Metallgesellschaft AG through using electrolysis of molten lithium chloride and potassium chloride.

It was apparently given the name "lithium" because it was discovered from a mineral while other common alkali metals were first discovered from plant tissue.

Occurrence

Lithium pellets (covered in white lithium hydroxide)
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Lithium pellets (covered in white lithium hydroxide)

Lithium is widely distributed but does not occur in nature in its free form. Because of its reactivity, it is always found bound with one or more other elements or compounds. It forms a minor part of almost all igneous rocks and is also found in many natural brines.

Since the end of World War II, lithium production has greatly increased. The metal is separated from other elements in igneous rocks, and is also extracted from the water of mineral springs. Lepidolite, spodumene, petalite, and amblygonite are the more important minerals containing it.

In the United States lithium is recovered from brine pools in Nevada. Today, most commercial lithium is recovered from brine sources in Chile. The metal, which is silvery in appearance like sodium, potassium and other members of the alkali metal series, is produced electrolytically from a mixture of fused lithium and potassium chloride. This metal cost about US$ 300 per pound ($650/kg) in 1997.

Isotopes

Naturally occurring lithium is composed of 2 stable isotopes Li-6 and Li-7 with Li-7 being the most abundant (92.5% natural abundance). Seven radioisotopes have been characterized with the most stable being Li-8 with a half-life of 838 ms and Li-9 with a half-life of 178.3 ms. All of the remaining radioactive isotopes have half-lifes that are less than 8.6 ms. The shortest-lived isotope of lithium is 4Li which decays through proton emission and has a half-life of 7.58043x10-23 s.

Lithium-7 is one of the primordial elements (produced in Big Bang nucleosynthesis). Lithium isotopes fractionate substantially during a wide variety of natural processes, including mineral formation (chemical precipitation), metabolism, ion exchange (Li substitutes for magnesium and iron in octahedral sites in clay minerals, where Li-6 is preferential over Li-7), hyperfiltration, and rock alteration.

Precautions

Like the other alkali metals, lithium in its pure form is highly flammable and slightly explosive when exposed to air and especially water. Lithium metal is also corrosive and requires special handling to avoid skin contact. Lithium should be stored in a non-reactive compound such as naptha or a hydrocarbon. Lithium compounds play no natural biological role and are considered to be slightly toxic. When used as a drug, blood concentrations of Li+ must be carefully monitored.

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