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 5p⁴
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, 6
Number of electrons in each shell, from the nucleus outwards.
449.5 °C (722.66 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.
988 °C (1,261 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).
6.232 g/cm³
Mass of one cubic centimetre of the substance. For gases, at 0 °C and standard pressure.
2.1 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.
9.01 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.
1.971 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.
138 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.
+6, +4, +2, -2
Charges the atom would have in its compounds if all its bonds were ionic; the main ones are listed.
Tellurium (Te) is a chemical element with atomic number 52. It sits in group 16 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 127.60.
Origin of the name
Tellurium is named after the Earth, Latin Tellus. In 1782 Franz Joseph Müller von Reichenstein, a mining official in Transylvania, extracted a strange metal from a gold ore and at first took it for antimony. His discovery was forgotten until 1798, when Martin Heinrich Klaproth isolated the element, named it and gave Müller the credit. When selenium was discovered in 1817, it was named after the Moon as tellurium’s companion.
Where is tellurium found?
Tellurium is occasionally found native, but more often combined with gold, as in calaverite. It is obtained as a by-product of copper refining.
What is tellurium used for?
A little tellurium makes copper and steel easier to machine and makes lead stronger. Bismuth telluride turns heat directly into electricity and back again, in thermoelectric coolers and generators, and tellurium is a semiconductor.
Interesting facts
People exposed to even tiny amounts of tellurium get ‘tellurium breath’, a strong smell of garlic.