This article picks up from Non-Linear Optimization using Extensions to LP and continues an exploration of what can be achieved using extensions to Linear Programming.
An anion is an ionic species having a negative charge. They are atoms that have gained electrons. Anions are one of the two types of ions. The other type is called a cation. Anions are attracted to the anode, while cations are attracted to the cathode. The concept of an anion is important in the corrosion industry because certain anions facilitate corrosion.
A counterion (pronounced as two words, i.e. counter ion, and sometimes written as two words) is the ion that accompanies an ionic species in order to maintain electric neutrality. In table salt (NaCl), the sodium cation is the counterion for the chlorine anion and vice versa. In a charged transition metal complex, a (i.e. non-coordinated) ion accompanying the complex is termed the counterion. In the older literature, the term gegenion (from gegen which means counter in German) is sometimes used.