Mercury

Mercury is one of only two metals that are liquid at room temperature (the other being gallium). The sight of its silvery, mirror-like pools rolling around freely has fascinated and terrified people for millennia. It is the most toxic heavy metal, causing irreversible neurological damage, yet it was once used in thermometers, barometers and even medicines.

  • Atomic Number8080 protons, 80 electrons
  • Atomic Mass200.59 u80× heavier than hydrogen
  • State at Room TempLiquidLiquid
  • Density13.5336 g/cm³
  • Melting / Boiling-38.8°C / 356.7°C
  • DiscoveredAncient

What is Mercury?

Mercury is a transition metal in Group 12 at the end of the d-block. With 80 protons, it has an anomalously low melting point (−38.8°C) due to relativistic effects that cause its electrons to contract. Its symbol Hg comes from the Latin hydrargyrum meaning liquid silver. Mercury dissolves many metals to form amalgams, and its vapour is poisonous.

Named after the Roman god Mercury, swift, mercurial, associated with communication and commerce. Known since antiquity: used in Chinese tombs and Egyptian cosmetics. The symbol Hg comes from the ancient Latin/Greek name hydrargyrum (water silver or liquid silver).

Fact The 2013 Minamata Convention, named after the Japanese city where mercury poisoning killed thousands in the 1950s, is an international treaty to reduce and eliminate mercury use globally. The Minamata disease disaster occurred when a chemical factory released methylmercury into the bay. Mercury concentrated in fish, then in people, causing a devastating neurological disease that still affects survivors today.

Where you find Mercury

On Earth

Cinnabar (mercury sulfide, HgS) is the primary ore. Spain (Almadén mine, now closed), China, Kyrgyzstan and Mexico are historical producers. Many uses are now banned.

How we use Mercury

  • Historically: thermometers, barometers, blood pressure monitors. Most now replaced due to toxicity.. Thermometers (historical)
  • Fluorescent and energy-saving light bulbs contain tiny amounts of mercury vapour that is essential for their operation.. Fluorescent lamps
  • Dental amalgam fillings contain mercury alloy, their safety is debated but they have been used for 150 years.. Dental amalgam
  • Chlor-alkali production, mercury cells were used to produce chlorine and sodium hydroxide, though now largely replaced.. Industrial chemistry
Did you know? The 2013 Minamata Convention, named after the Japanese city where mercury poisoning killed thousands in the 1950s, is an international treaty to reduce and eliminate mercury use globally. The Minamata disease disaster occurred when a chemical factory released methylmercury into the bay. Mercury concentrated in fish, then in people, causing a devastating neurological disease that still affects survivors today.

How it was discovered

Named after the Roman god Mercury, swift, mercurial, associated with communication and commerce. Known since antiquity: used in Chinese tombs and Egyptian cosmetics. The symbol Hg comes from the ancient Latin/Greek name hydrargyrum (water silver or liquid silver).

Deeper dive: mercury properties and applications

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Moving to 81 protons on the periodic table takes us to the next element.