The strength of an ionic bond is influenced primarily by the charge and size of the ions involved.

Ionic bonding is a type of chemical bond characterized by the electrostatic attraction between oppositely charged ions. This type of bond forms when metal atoms lose one or more of their outer electrons, resulting in the formation of positive ions, while non-metal atoms gain one or more electrons, becoming negative ions. The strength of the ionic bond that forms between these ions depends on two key factors: the charge of the ions and their sizes.

Firstly, the charge of the ions significantly affects the strength of the ionic bond. A higher charge on the ions leads to a stronger ionic bond due to the increased electrostatic attraction between the oppositely charged ions. For example, an ionic bond between a $+2$ ion and a $-2$ ion will be stronger than one formed between a $+1$ ion and a $-1$ ion.

Secondly, the size of the ions is also critical in determining the strength of the ionic bond. Smaller ions can approach each other more closely than larger ions, which enhances the electrostatic attraction and results in a stronger ionic bond. As such, an ionic bond formed between two smaller ions will typically be stronger than one between two larger ions.

In conclusion, the strength of an ionic bond is determined by both the charge and size of the ions involved. Specifically, the greater the charge and the smaller the size of the ions, the stronger the ionic bond will be. Understanding these factors can assist in predicting the strength of ionic bonds in various compounds.