80 Hg 200.592

Mercury

Transition metal Hydrargyrum liquid

[Xe] 4f¹⁴ 5d¹⁰ 6s² · 2 · 8 · 18 · 32 · 18 · 2

← Au Gold Tl Thallium →

The only metal liquid at room temperature and one of the more insidious poisons. Mercury fascinated alchemists and physicians for millennia and became, in the twentieth century, the emblem of industrial poisoning.

3D model

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

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Atomic properties

Atomic number: 80
Atomic mass: 200.592 а.е.м.
Electron configuration: [Xe] 4f¹⁴ 5d¹⁰ 6s²
Electrons per shell: 2 · 8 · 18 · 32 · 18 · 2
Block: d-block
Group: Zinc group
Period: 6
Electronegativity (Pauling): 2
Electronegativity (Allen): 1.76
Atomic radius: 171 pm
Covalent radius: 132 pm
Van der Waals radius: 155 pm
Ionisation energy 1: 1 007.1 kJ/mol
Ionisation energy 2: 1 810 kJ/mol
Ionisation energy 3: 3 300 kJ/mol
Electron affinity: 0 kJ/mol
Common oxidation states: +1, +2
Oxidation states: -2, +1, +2

Physical properties

State at 25 °C: liquid
Density: 13.534 g/cm³
Melting point: 234.32 K · -38.8 °C
Boiling point: 629.88 K · 356.7 °C
Speed of sound: 1 451.4 m/s

Thermal properties

Heat of fusion: 2.29 kJ/mol
Heat of vaporisation: 59.11 kJ/mol
Specific heat capacity: 0.14 J/(g·K)
Thermal conductivity: 8.3 W/(m·K)

Mechanical properties

Young's modulus: no data
Shear modulus: no data
Bulk modulus: 25 GPa
Poisson ratio: no data
Mohs hardness: no data
Brinell hardness: no data

Electrical and magnetic properties

Electrical resistivity: 961 nΩ·m
Magnetic ordering: diamagnetic
Curie point: no data
Néel point: no data
Superconducting point: 4.15 K

Crystal structure

Crystal structure: rhombohedral
Lattice constants: a = 346.5 pm

Abundance

In the crust: 0.085 mg/kg
In the ocean: 3·10⁻⁵ mg/L
In the universe: 0.01 mg/kg
In the human body: 0 mg/kg

Isotopes

Isotope	Abundance	Half-life	Decay mode
¹⁹⁶Hg	0.15 %	stable	—
¹⁹⁸Hg	9.97 %	stable	—
¹⁹⁹Hg	16.87 %	stable	—
²⁰⁰Hg	23.1 %	stable	—
²⁰¹Hg	13.18 %	stable	—
²⁰²Hg	29.86 %	stable	—
²⁰⁴Hg	6.87 %	stable	—

Seven stable isotopes. Mercury-197 was used in kidney scintigraphy before technetium agents.

Discovery

Year of discovery: known since antiquity
Discovered by: known since antiquity
Where: no data
Origin of the name: the symbol Hg is from Greek hydrargyros (liquid silver); named after the planet Mercury

History

Mercury has been found in Egyptian tombs from the sixteenth century BCE. Alchemists took it for the first principle of all metals. The symbol Hg is from Greek hydrargyros, liquid silver.

Where it occurs

0.085 mg/kg of the crust. The main mineral is cinnabar, HgS; the Almadén deposit in Spain was worked for two thousand years.

How it is produced

By roasting cinnabar: the sulfide breaks down, the mercury volatilises and is condensed. Production fell sharply after the 2013 Minamata Convention.

Role in living things

No biological role. Methylmercury, made by bacteria from inorganic mercury, accumulates up the food chain and reaches dangerous levels in predatory marine fish.

Safety

Mercury vapour attacks the nervous system; chronic poisoning causes tremor and personality change — mad hatter's disease came from mercuric nitrate used in felting. Minamata disease in Japan was mass methylmercury poisoning through fish.

Uses

Fluorescent lamps: mercury vapour emits ultraviolet that a phosphor turns into light
Mercury-cell chloralkali electrolysis (being phased out)
Dental amalgams
Scientific instruments: barometers, thermometers, diffusion pumps (largely historical)

Curiosities

Mercury is the only metal liquid at room temperature, because relativistic effects weaken its metallic bonding.
"Mad as a hatter" comes from mercury poisoning among felt workers.
The 2013 Minamata Convention is the first global treaty banning the use of a specific chemical element.
Mercury freezes at −39 °C, which is why mercury thermometers do not work in Yakutia.