Chemical compounds and chemical bonds. The term valence is what chemists use to describe chemical bonding. Electrovalence describes bonding in ionic compounds. It is also equal to the oxidation number of the ion.
Covalence describes bonding in molecular compounds.
Oxidation number rules for Elements and Monoatomic Ions. The oxidation number of any element is zero. The oxidation number of any monoatomic ion is the same as the charge on this ion. Oxidation removal of electrons. Reduction gain of electrons.