3 Li 6.94

Lithium

Alkali metal Lithium solid

[He] 2s¹ · 2 · 1

← He Helium Be Beryllium →

The lightest metal and the lightest solid element: lithium floats not only on water but on kerosene. One loosely held electron makes it chemically lively, and a high electrochemical potential makes it indispensable in batteries.

3D model

Bohr model: nucleus and electron shells from the real configuration. Valence electrons are highlighted.

Drag to rotate, scroll to zoom

Atomic properties

Atomic number: 3
Atomic mass: 6.94 а.е.м.
Electron configuration: [He] 2s¹
Electrons per shell: 2 · 1
Block: s-block
Group: Alkali metals
Period: 2
Electronegativity (Pauling): 0.98
Electronegativity (Allen): 0.91
Atomic radius: 167 pm
Covalent radius: 128 pm
Van der Waals radius: 182 pm
Ionisation energy 1: 520.2 kJ/mol
Ionisation energy 2: 7 298.1 kJ/mol
Ionisation energy 3: 11 815 kJ/mol
Electron affinity: 59.6 kJ/mol
Common oxidation states: +1
Oxidation states: +1

Physical properties

State at 25 °C: solid
Density: 0.534 g/cm³
Melting point: 453.65 K · 180.5 °C
Boiling point: 1 603 K · 1 329.9 °C
Speed of sound: 6 000 m/s

Thermal properties

Heat of fusion: 3 kJ/mol
Heat of vaporisation: 136 kJ/mol
Specific heat capacity: 3.582 J/(g·K)
Thermal conductivity: 84.8 W/(m·K)

Mechanical properties

Young's modulus: 4.9 GPa
Shear modulus: 4.2 GPa
Bulk modulus: 11 GPa
Poisson ratio: no data
Mohs hardness: 0.6
Brinell hardness: 5 MPa

Electrical and magnetic properties

Electrical resistivity: 92.8 nΩ·m
Magnetic ordering: paramagnetic
Curie point: no data
Néel point: no data
Superconducting point: no data

Crystal structure

Crystal structure: body-centred cubic (bcc)
Lattice constants: a = 351 pm

Abundance

In the crust: 20 mg/kg
In the ocean: 0.18 mg/L
In the universe: 6 mg/kg
In the human body: 0.03 mg/kg

Isotopes

Isotope	Abundance	Half-life	Decay mode
⁶Li	7.59 %	stable	—
⁷Li	92.41 %	stable	—

Both stable isotopes have industrial value: lithium-6 makes tritium, lithium-7 controls coolant chemistry in nuclear reactors.

Discovery

Year of discovery: 1817
Discovered by: Johan August Arfwedson
Where: Sweden
Origin of the name: from Greek lithos (stone): unlike sodium and potassium it was found in a mineral

History

Johan Arfwedson found a new element in 1817 in petalite from the Utö mine. It was named from the Greek for stone — unlike sodium and potassium, known from plant ashes, lithium was first found in a mineral.

Where it occurs

20 mg/kg in the crust, mostly in the pegmatite minerals spodumene and lepidolite. The largest commercial reserves are the salt-flat brines of the lithium triangle in Chile, Bolivia and Argentina.

How it is produced

From brine by solar evaporation over months, then precipitation as the carbonate. From ore by roasting spodumene with sulfuric acid. The metal itself comes from electrolysis of molten LiCl–KCl.

Role in living things

Not considered an essential trace element, but lithium salts are one of the few psychiatric treatments shown to reduce suicide risk. The therapeutic window is narrow, so blood levels have to be monitored.

Safety

Lithium metal reacts violently with water and ignites in damp air. Overdosing on lithium salts causes tremor and damages the kidneys and thyroid.

Uses

Lithium-ion batteries — phones, electric cars, grid storage
Lithium carbonate in psychiatry as a mood stabiliser for bipolar disorder
Lithium greases, which hold up across a wide temperature range
An additive in glass and ceramics to cut thermal expansion
Lithium-6 deuteride as thermonuclear weapon fuel

Curiosities

Lithium, with hydrogen and helium, was made in the first minutes after the Big Bang; every other element was built by stars.
At 0.534 g/cm³ lithium is half as dense as water.
A lithium battery is not the same as a lithium-ion battery: the first is single-use, the second rechargeable.
Lithium colours a flame carmine red, which is why fireworks use it.
The universe holds about a third of the lithium Big Bang theory predicts; the discrepancy is still unexplained.