Polyatomic ions are tightly bound groups composed of multiple elements that possess an overall charge. The positively charged ions are called cations, while the negatively charged ions are called anions.
The charts below show some of the most common polyatomic ions grouped by their respective charges. Unfortunately when it comes to learning them all you will have to sit down and memorize.
The one major +1 charge polyatomic ion is the ammonium ion.
The +2 charge cation is the mercury (I) ion, which is composed of two mercury ions that are bonded together to form a dimer.
There are many - 1 charge anions and these are the most commonly recognized.
Polyatomic ions containing halogens are referred to as oxyhalogens or halogen oxyanions.
The most common – 2 charge polyatomic ions are:
The most common – 3 charge polyatomic ions are:
Memorizing these polyatomic ions will be essential later on when dealing with naming binary molecular compounds, naming ionic compounds, and naming oxyacids. In addition our review on the various charges will be further discussed when calculating oxidation states and oxidation numbers.