The ionic bond is a result of the change between ions of opposite electric charges (anions and cations). This link usually happens between metals and nonmetals.
Metals - 1 to 3 electrons in the last shell; tendency to lose electrons and form cations. More electropositive or less electronegative elements.
Nonmetals - 5 to 7 electrons in the last shell; tendency to gain electrons and form anions. More electronegative or less electropositive elements. So:
METAL + NON METAL → ION CONNECTION
Example: Na and Cl
Na (Z = 11) K = 2 L = 8 M = 1
Cl (Z = 17) K = 2 L = 8 M = 7
Na wants to donate 1 is → Na + (cation)
Cl wants to receive 1 is → Cl - (anion)
Chlorine wants to receive 7 is in the last layer. To get 8e (same as the noble gases), you need 1e.
Ionic bonds form ionic compounds that are made up of cations and anions. Such ionic compounds form according to the ability of each atom to gain or lose electrons. This ability is the valence.
Observe the table with the valence of the chemical elements (some alkaline, earth alkaline, calcogen and halogen):
Valence of other chemical elements:
Example: Mg and Cl
You can use the “scissor rule”, Where the cation will be the number of chlorines (not metal) in the final formula and the anion will be the number of magnesium (metal).
Another example: Al and O
In this case, the “scissors rule” was also used. The final formula will be called ion formula.
Electronic Formula / Lewis Theory
The electronic formula represents the electrons in the valence layers of atoms.
The electronic formula is also called the formula of Lewis, because it was proposed by this scientist.