The charge of a strontium ion is +2. The charge of an ion is determined by the ratio of the number of electrons to the number of protons, so an ion with a charge of +2 has two more protons than electrons.
An ion of strontium contains 38 protons and 36 electrons, whereas an uncharged, nonionic strontium atom contains 38 electrons and 38 protons. A cation is an ion with fewer electrons than protons, for in the strontium ion. A strontium ion is a monatomic ion, which means that it consists of a single atom.
