Positive and negative ions form when a metalShiny element that is a good conductor of electricity and heat, and which forms basic oxides. reacts with a non-metalElement that is a poor conductor of electricity and heat, and which forms acidic oxides., by transferring electronSubatomic particle, with a negative charge and a negligible mass relative to protons and neutrons.. The oppositely charged ions are strongly attracted to each other, forming ionic bondingIonic bonding forms between two atoms when an electron is transferred from one atom to the other, forming a positive-negative ion pair..
Dot and cross diagrams
A dot and cross diagram models the transfer of electrons from metal atomThe smallest part of an element that can exist. to non-metal atoms. The electrons from one atom are shown as dots, and the electrons from the other atom are shown as crosses. For example, when sodium reacts with chlorine, electrons transfer from sodium atoms to chlorine atoms. The diagrams show two ways of representing this electron transfer.
Modelling ionic bonding
The slideshow shows dot and cross diagrams for the ions in sodium chloride, magnesium oxide and calcium chloride.