- Cations are positively charged ions. Examples of Cations are Na+, Mg+2 and Al+3.
- Cations are formed by the loss of one or more electrons from the outer shell or orbit of atoms to achieve their octet or duplet.
- Number of electron in a cation is less than the number of proton in that cation. For example Na+ has 10 elections and 11 protons.
- Ionic radii of cations decrease with increase in positive charges. For example Ionic radius of Na+ is more than that of Mg+2.
- Ionic size of a cation is always smaller than its parent atom. Because effective nuclear charge increases. For example Ionic size K+ is less than atomic size of K.
- Cations are ions of metals.
- Anions are negatively charged ions. Examples of Anions are F–, O-2 and N-3.
- An anion is formed by gaining one or more electrons in their valence shell to complete their octet or duplet.
- Number of electrons in an anion is more than the number of protons in it. For example Cl has 17 electrons as well as 17 proton but Cl– has 18 electrons and 17 protons.
- Ionic radii of anion increase with decrease in negative charges. Thus Cl– will have higher Ionic radius than that of S-2.
- Ionic size of anions are larger than their parent atoms. Because effective nuclear charge decreases. Ionic size of Cl– is larger than atomic size of Cl.
- Anions are ions of non-metals.