When two or more elements react together, compounds are formed. The atoms of elements join together by sharing electrons or transferring them to achieve stable electronic structures. When atoms of non-metals join together by sharing electrons, covalent bonds are formed.
When metallic elements react with non-metallic elements they produce ionic compounds. The metal atoms lose electrons to form positive ions. The atoms of non-metals gain electrons to form negative ions. The ions have the stable electronic structure of a noble gas. The oppositely charged ions attract each other strongly in the ionic compound. This is called ionic bonding.
Elements in Group 1 of the periodic table have one electron in the highest occupied energy level. Sodium atoms, Na (electronic structure 2,8,1) form sodium ions, Na+ (2,8). Elements in Group 7 of the periodic table have seven electrons in the highest occupied energy level. Chlorine atoms, Cl (2,8,7) from chloride ions, Cl- (2,8,8). The compound sodium chloride has equal numbers of sodium and chloride ions so we write its formula as NaCl.
Ionic bonding holds oppositely charged ions together in giant structures. The giant structure of ionic compounds is very regular because the ions pack together neatly. Strong electrostatic forces of attraction…