what is an ion

An ion is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convention. An atom can acquire a positive charge or a negative charge depending on whether the number of electrons in an atom is greater or less than the number of protons in the atom. When an atom is attracted to another atom because it has an unequal number of electrons and protons, the atom is called an ion. If the atom has more electrons than protons, it is a negative ion, or an anion. If it has more protons than electrons, it is a positive ion, or a cation. Ions consisting of only a single atom are termed atomic or monatomic ions, while two or more atoms form molecular ions or polyatomic ions. Ions can be non-chemically prepared using various ion sources, usually involving high voltage.