What is ionic and covalent bonding?
Ionic bonding occurs when a metal and non-metal react together. It involves the metal atom losing electrons from its outer shell to become a positive ion (as there are more positive protons in the nucleus, than negative electrons). These electrons are transferred to the non metal atom, which gain electrons to become a negative ion (as there are more electrons than protons). There is a strong electrostatic attraction between the positive metal ion and negative non-metal ion, which is the ionic bond. The reason atoms want to gain or lose electrons is to get a full outer shell of electrons (8) as they are more stable in this formation. Metal atoms are on the left hand side of the periodic table and can be found in groups 1 or 2, and so have 1 or 2 electrons in their outer shell respectively. It is therefore easy for these atoms to lose electrons to become positive ions and gain a full outer shell. Non metals are on the right hand side of the periodic table, for example in groups 6 or 7 and so need to gain either 1 or 2 electrons to gain a full outer shell, whcih they can obtain from metals. Covalent bonds, on the other hand, occurs between non metal atoms and involves atoms sharing a pair of electrons in order to gain a full outer shell. For example, two chlorine atoms display covalent bonding to produce a molecule of chlorine: Cl2. Each chlorine atom has 7 electrons in its outer shell. Each chlorine atom donates 1 electron to the pair, which is shared between the two atoms to ensure they both have a full outer shell of electrons, and are in effect both gaining one extra electron. There is a strong electrostatic attraction between the positive nucleus of the atoms and the shared pair of electrons, which is what the covalent bond is, and is very strong and requires a lot of energy to break
