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.
[Kr] 5s² 4d¹⁰ 5p³
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, 18, 5
Number of electrons in each shell, from the nucleus outwards.
630.6 °C (903.78 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.
1,587 °C (1,860 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).
6.685 g/cm³
Mass of one cubic centimetre of the substance. For gases, at 0 °C and standard pressure.
2.05 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.
8.608 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.
1.047 eV
Energy released when a neutral atom gains an electron. Highest for the halogens. Noble gases, nitrogen and some metals form no stable negative ion.
139 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.
+5, +3, -3
Charges the atom would have in its compounds if all its bonds were ionic; the main ones are listed.
Antimony (Sb) is a chemical element with atomic number 51. It sits in group 15 and period 5 of the periodic table, in the p-block. It is a metalloid. At room temperature it is a solid. Its standard atomic weight is 121.76.
Origin of the name
The origin of the name antimony is uncertain; it is often explained as the Greek anti + monos, ‘not alone’, because the element is almost never found by itself. The symbol Sb comes from the Latin stibium, the name of the black mineral stibnite, which the ancient Egyptians ground up and used as the eye make-up kohl.
Where is antimony found?
Antimony occurs in more than a hundred minerals, but almost all of it comes from stibnite, an antimony sulfide; now and then it is found as the native element.
What is antimony used for?
Antimony hardens lead: alloys of the two go into car batteries, bullets and bearings. Antimony trioxide makes plastics and fabrics harder to set alight, and very pure antimony is used in semiconductors.
Interesting facts
Antimony and many of its compounds are poisonous, although they were long taken as medicines.