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J Metals and Non-metals “ 231 ERE] IONIC BOND (OR ELECTROVALENT BOND) The chemical bond formed by the transfer of electrons from one atom to another is known as an ionic bond or electrovalent bond. The transfer of electrons takes place in such a way that the ions formed have stable electronic configuration of an inert gas. | Metals usually have 1, 2 or 3 electrons in their outermost shells which they can donate to form stable positive ions On the other hand, non-metals have usually 5, 6 or 7 electrons in their outermost shell, so they gain electrons to form stable negative ions. The force of attraction which holds these oppositely charged ions constitutes the ionic bond. The compounds containing tonic bond are called ionic compounds. They are made up of ions. 3.12.1 Examples of Ionic Compounds 1. Formation of Sodium Chloride (NaCl) ‘Atomic number of sodium (N: a)=11 ~ Its electronic configuration = 2, 8,1 Sodium has only one electron in its valence shell. Therefore, it loses this electron to ac configuration 2, 8 (similar to that of neon) to form sodium ion (Nat). quire the stable electronic Na* “ ec Na* Sodium atom Sodium ion Flectronic configuration (2,8,1) (2,8) (Unstable electronic configuration) (Stable electronic configuration) Atomic number of chlorine (Cl) = 17 . Its electronic configuration = 2, 8, 7 Chlorine has 7 electrons in its valence shell. 2, 8, 8 (similar to that of oxygen) and form chloride ion (CI). So it gains one electron to acquire the stable electronic configuration of Chlorine — Electron. Chloride ion atom (2, 8, 8) 2, 8,7) | | | | | | | | Sodium ions have positive charge whereas chloride ions have negative charge. These oppositely charged ions are held together by electrostatic forces of attraction forming the compound Na*Cl- or simply written as NaCl. The formation of sodium chloride may be represented as follows : Electron transferred Na” — Nat fC] or NaCl Sodium atom Chlorine atom Sodium ion Chloride ion (2, 8, 1) (2, 8,7) (2, 8) (2, 8, 8) 
