Average mass of an atom in unified atomic mass units (1 u is 1/12 of the mass of a carbon-12 atom). Accounts for the natural mix of the element’s isotopes.
Number of the vertical column, 1 to 18 in IUPAC numbering. Elements in a group share the same outer-shell layout, so their properties are alike.
Number of the horizontal row. Usually equal to the number of electron shells in the atom; palladium is the exception, with four shells in period 5.
The subshell (s, p, d or f) that receives the last electrons in the usual filling order; it divides the table into four blocks. Real atoms sometimes differ: lanthanum starts the f-block but has no f electrons.
[Xe] 6s² 4f¹⁴ 5d¹⁰
How electrons are arranged in subshells. The bracket stands for the previous noble gas; the superscript is the number of electrons in a subshell.
2, 8, 18, 32, 18, 2
Number of electrons in each shell, from the nucleus outwards.
-38.8 °C (234.32 K)
Temperature at which the solid turns liquid at standard pressure. Helium, carbon and arsenic do not melt at normal pressure: helium needs about 25 atm, carbon and arsenic turn straight into vapour.
356.7 °C (629.88 K)
Temperature at which the liquid boils at standard pressure. For carbon and arsenic, the temperature at which the solid turns straight into vapour (sublimation).
13.534 g/cm³
Mass of one cubic centimetre of the substance. For gases, at 0 °C and standard pressure.
2.00 Pauling
How strongly an atom pulls electrons towards itself in a chemical bond. On the Pauling scale it runs from 0.79 for caesium to 3.98 for fluorine.
10.438 eV
Energy needed to remove the most loosely bound electron from an atom. The lower it is, the more easily the element gives up an electron, which is typical of metals.
no stable negative ion
Energy released when a neutral atom gains an electron. Highest for the halogens. Noble gases, nitrogen and some metals form no stable negative ion.
132 pm
Half the length of a single covalent bond between two atoms of the element. It shows the size of an atom inside a molecule or crystal: 76 pm for carbon, 132 pm for iron.
+2, +1
Charges the atom would have in its compounds if all its bonds were ionic; the main ones are listed.
Mercury (Hg) is a chemical element with atomic number 80. It sits in group 12 and period 6 of the periodic table, in the d-block. It is a transition metal. At room temperature it is a liquid. Its standard atomic weight is 200.59.
Origin of the name
Mercury is named after the Roman god Mercury, the swift messenger of the gods. The symbol Hg comes from hydrargyrum, ‘water-silver’. Mercury was known to the ancient Chinese and Indians and has been found in Egyptian tombs.
Where is mercury found?
Mercury is only rarely found as the liquid metal in nature. It is obtained mainly from cinnabar, a bright red mineral of mercury sulfide, by heating it and condensing the vapour.
What is mercury used for?
Mercury was long used in thermometers and barometers and is still used in some lamps. With other metals it forms amalgams: silver amalgam has filled teeth, and gold amalgam helps extract gold from ore. Because mercury is poisonous, many of these uses are being phased out.
Interesting facts
Mercury is the only metal that is liquid at ordinary room temperature: it freezes only at about −39 °C.
Mercury and its compounds are poisonous and build up in the body. Factory waste containing mercury caused mass poisoning around Minamata Bay in Japan.