Nonmetals form negative ions (anions). A nitrogen atom must gain three electrons to have the same number of electrons as an atom of the following noble gas, neon. Thus, a nitrogen atom will form an anion with three more electrons than protons and a charge of 3−.
A molecular structure is a shape of a molecule, a three-dimensional shape or configuration of a molecule that is dependent on the preferred spatial orientation of covalent bonds to atoms having two or more partners. Attached is the diagram for the molecular structure of So42 .
The statement is implying that this is the only way to obtain a salt. Any ionic compound is a salt. For example, NaCl (table salt) is an ionic compound. It is the combination of a nonmetal (Cl) and a metal (Na).