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.
[Rn] 7s² 5f¹⁴ 6d³ predicted
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, 32, 11, 2
Number of electrons in each shell, from the nucleus outwards.
no data
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.
no data
Temperature at which the liquid boils at standard pressure. For carbon and arsenic, the temperature at which the solid turns straight into vapour (sublimation).
no data
Mass of one cubic centimetre of the substance. For gases, at 0 °C and standard pressure.
no data
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.
no data
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 data
Energy released when a neutral atom gains an electron. Highest for the halogens. Noble gases, nitrogen and some metals form no stable negative ion.
no data
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
Charges the atom would have in its compounds if all its bonds were ionic; the main ones are listed.
Discovered
1970
Discovered by
Joint Institute for Nuclear Research and Lawrence Berkeley National Laboratory
Dubnium (Db) is a chemical element with atomic number 105. It sits in group 5 and period 7 of the periodic table, in the d-block. It is a transition metal. At room temperature it is predicted to be a solid. It has no standard atomic weight; the mass number of its most stable isotope is 268.
Origin of the name
Dubnium is named after Dubna, the town near Moscow that is home to the Joint Institute for Nuclear Research. Scientists there reported element 105 in 1967, and a group at Berkeley made it in 1970 and wanted to call it hahnium, after Otto Hahn. After a long dispute, the name dubnium was chosen in the 1990s.
Where is dubnium found?
Dubnium does not exist in nature. It is made in particle accelerators, a few atoms at a time.