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] 5s¹ 4d⁴
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, 12, 1
Number of electrons in each shell, from the nucleus outwards.
2,477 °C (2,750 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.
4,744 °C (5,017 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).
8.57 g/cm³
Mass of one cubic centimetre of the substance. For gases, at 0 °C and standard pressure.
1.6 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.
6.759 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.
0.917 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.
164 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
Charges the atom would have in its compounds if all its bonds were ionic; the main ones are listed.
Niobium (Nb) is a chemical element with atomic number 41. It sits in group 5 and period 5 of the periodic table, in the d-block. It is a transition metal. At room temperature it is a solid. Its standard atomic weight is 92.906.
Origin of the name
In 1801 Charles Hatchett found a new element in a black mineral that had been sent to England from Connecticut many years before, and called it columbium. Soon William Hyde Wollaston declared it to be the same as tantalum, and only decades later Heinrich Rose showed that tantalum ores hold a second, very similar element. He named it niobium, after Niobe, the daughter of Tantalus in Greek myth. The two names lived side by side for a century until IUPAC chose niobium, though American metallurgists still often say columbium.
Where is niobium found?
Niobium is mined mainly from the minerals pyrochlore and columbite. The largest deposits are in Brazil.
What is niobium used for?
Most niobium goes into steel: a tiny addition makes it much stronger, for example in gas pipelines. Niobium alloys withstand heat in jet and rocket engines. Niobium-titanium wire becomes a superconductor when cooled with liquid helium and is wound into powerful magnets, and superconducting niobium cavities speed up particles in accelerators. It is also used in jewellery.
Interesting facts
Niobium and tantalum are so alike, and so often found together, that chemists argued for decades whether they were one element or two.