They are generally formed when nonmetals and metals bond. To determine which substance is formed, we must use the charges of the ions involved. In order to create a neutral charged molecule, you must combine the atoms in certain proportions. Scientists use subscripts to identify how many of each atom makes up the molecule. Knowledge of the charges of ions is crucial to knowing the formulas of the compounds formed.
Isomers are compounds with the same molecular formula, but different arrangments of atoms.
Thus, it is important to include some signal within the name of the ion that identifies which arrangement you are talking about. There are three main types of classification, geometric, optical and structural isomers. Geometric isomers refers to which side of the ion atoms lie. The prefixes used to distinguish geometric isomers are cis meaning substituents lie on the same side of the ion and trans meaning they lie on opposite sides. Below is a diagram to help you remember.