ChemSphere
80Hg200.592

Mercury

Transition metal · Period 6 · Group 12 · d-block

The only metal that is liquid at room temperature

Atomic mass
200.592 u
State at 25 °C
Liquid
Electronegativity
2
Melting point
-38.8 °C
Boiling point
356.7 °C
Configuration
[Xe] 4f14 5d10 6s2
Building atom…
80 protons 121 neutrons 80 electrons

Nucleus drawn at reduced count for clarity. Drag to rotate.

Mercury, explained

Video lesson in production

Bhavya’s explainer for this element will play here.

Overview

Mercury is the only metal that is liquid at room temperature, melting at −38.8 °C. Its configuration is [Xe]4f14 5d10 6s2, with full d and s subshells. Relativistic effects contract and stabilise the 6s orbital, holding the two 6s electrons so tightly that they barely participate in metallic bonding. The atoms are therefore only weakly attracted to one another, which is why mercury melts so low and why its vapour is made of single atoms, like a noble gas.

Mercury dissolves many metals, including gold, silver, tin and zinc, to form alloys called amalgams. It has two common oxidation states: +2, as in HgO and HgS, and +1, which exists as the unusual Hg₂²⁺ ion with a direct mercury–mercury bond. Mercury vapour emits ultraviolet light when an electric current passes through it, the basis of fluorescent lamps. Microbes in water convert mercury into methylmercury, which accumulates in fish and is a potent neurotoxin.

Discovery

Mercury has been known since antiquity; a vessel of it was found in an Egyptian tomb dating to about 1500 BCE, and ancient Chinese, Greek and Roman writers described it. It was made by heating the red mineral cinnabar. The symbol Hg comes from the Latin hydrargyrum, from the Greek for 'water-silver'. Alchemists linked it with the planet Mercury, the fastest-moving planet, a name that suited the quick, mobile metal.

Where it’s found
About 0.08 parts per million of Earth's crust, obtained mainly by roasting cinnabar (HgS) and as a by-product of gold and zinc processing.
What it’s used for
  • Fluorescent lamps
  • Chlor-alkali electrolysis (phasing out)
  • Dental amalgam
  • Thermometers and barometers (historic)
  • Gold extraction by amalgamation
In living things
No biological role; mercury and especially methylmercury are highly toxic to the nervous system, kidneys and developing fetuses.
Safety
Highly toxic; mercury vapour is readily absorbed through the lungs, so spills must be cleaned up promptly with proper ventilation and never vacuumed.

How it compares

Where Mercury sits among all 118 elements on the trends that shape the table.

  • Electronegativity2Pauling

    #31 of 100 elements with data

  • Ionization energy1,010kJ/mol

    #16 of 104 elements with data

  • Atomic radius150pm

    #44 of 95 elements with data

  • Electron affinity-48kJ/mol

    #95 of 109 elements with data

  • Density13.5g/cm³

    #25 of 114 elements with data

  • Melting point234K

    #99 of 110 elements with data

Density
13.5 g/cm³
Atomic radius
150 pm
Covalent radius
133 pm
Molar heat
27.983 J/(mol·K)
Appearance
silvery
Discovered by
unknown, before 2000 BCE

Inside the atom

80 electrons arranged in 6 shells: 2 · 8 · 18 · 32 · 18 · 2.

Orbital diagram

1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 · shorthand [Xe] 4f14 5d10 6s2

  1. 1s2
  2. 2s2
  3. 2p6
  4. 3s2
  5. 3p6
  6. 4s2
  7. 3d10
  8. 4p6
  9. 5s2
  10. 4d10
  11. 5p6
  12. 6s2
  13. 4f14
  14. 5d10

Each box is an orbital holding up to two electrons of opposite spin. Highlighted subshells hold the valence electrons that decide how Mercury bonds.

Ionization energies

Energy to remove each electron in turn, on a log scale. Each electron is harder to remove than the last, because the remaining ones feel more of the nucleus.

Signature reactions

The chemistry Mercury is known for.

  1. Redox · Metal extraction

    Roasting cinnabar

    Heating cinnabar in air releases mercury vapour, which is condensed into liquid metal, while the sulfur leaves as sulfur dioxide. This simple process has been used for over two thousand years.

    HgS(s)+O2(g)Hg(g)+SO2(g)

    Conditions: about 600 °C in air

  2. Redox · Thermal decomposition

    Decomposition of mercury(II) oxide

    Red mercury(II) oxide breaks down into droplets of mercury and oxygen gas. Joseph Priestley used this reaction in 1774 to isolate oxygen, and Lavoisier used it to understand combustion.

    2HgO(s)2Hg(l)+O2(g)

    Conditions: heating above about 450 °C

  3. Redox · Disproportionation

    Calomel with ammonia

    White calomel turns black when ammonia is added, as Hg(I) splits into mercury metal and white HgNH2Cl. In classical qualitative analysis this colour change confirmed mercury(I) in a sample.

    Hg2Cl2(s)+2NH3(aq)Hg(l)+HgNH2Cl(s)+NH4+(aq)+Cl−(aq)

    Conditions: aqueous ammonia, room temperature

Where you’ll meet it

  • Cinnabar

    Cinnabar

    This bright red mercury sulfide is the main ore of mercury and an ancient pigment.

    Photo: Wikimedia Commons
  • Mercury-in-glass thermometer

    Mercury-in-glass thermometer

    Mercury's steady expansion with temperature made it the standard thermometer liquid for centuries.

    Photo: Wikimedia Commons
  • Almadén

    Almadén

    This Spanish town sat atop the world's largest mercury deposit, mined since Roman times.

    Photo: Wikimedia Commons
  • Fluorescent lamp

    Fluorescent lamp

    An electric discharge through mercury vapour produces the UV light that makes the lamp's phosphor coating glow.

    Photo: Wikimedia Commons

Research

No research on Mercury yet

When Bhavya publishes a project that studies Mercury, it will be linked here.

See all research