Ionic bonds hold atoms together using the electrostatic charge between their positive and negative ions. These ions are formed when electrons are transferred between atoms, the net loss or gain determining if the ion is positive, called a cation, or negative, an anion.
When elements combine through ionic bonding, they will form the ion that is the most stable. This means the ion for which creation involves the most energy by giving away as many electrons as possible. The energy needed to remove electrons from atoms is called ionisation energy. The amount of ionisation energy required increases with each electron removed and lower-level electrons require much more energy to remove as they are closer to the nucleus. This limits the ions that atoms can become, preventing them from discarding all of their electrons. The main way to depict ionic bonds is the Lewis diagram which shows electron transfer, polarity and the product of the bonding. Ionic bonding was first theorized by British physicist Joseph John Thomson in 1897, after he had discover the electron. He suggested in a scientific paper that electrons could be transferred between atoms, giving them a form of magnetic charge between the new positive or negatively charged atoms.