A set of neighbouring groups on the periodic table.
block
The negative charge that occurs when an atom receives an extra electron and becomes a negative ion.
electron affinity
The path an electron follows as it revolves round the nucleus.
Electron shell/orbit
A horizontal row of elements in the periodic table.
Period
Elements found in the same column of the periodic table.
Group or family
A measurement of distance between the outer boundary of an atom’s electron cloud and its nucleus.
Atomic radius
The minimum amount of energy required to remove an electron from an atom.
ionization energy
One or two-letter designation referring to an element.
Element symbol
An atom’s outermost electron shell.
valence shell
A system that shows how electrons are distributed in an atom’s orbitals.
Electron configuration