5.6 METALLIC BONDS

A special type of bonding occurs in metals. In metals, the valence electrons are not confined to individual atoms. These electrons are called free electrons. Metal atoms lose these electrons and form positive ions. The free electrons can move throughout the entire metal structure.

Delocalised Electrons

This leads to the formation of a sea of delocalized electrons called the electron sea. The metal cations are held together by the strong electrostatic attractive forces between the metal cations and negatively charged electron sea. This force gives metals their unique properties. This type of bonding is called metallic bonding.

Properties of Metals

• Malleability
• Ductility
• High melting and boiling point
• High electrical and thermal conductivity
• Metallic lustre

Structure and Properties of Metals Suitable for Industrial Purposes

Metals have giant structures. The metallic bond is strong, resulting in very high melting and boiling points, which makes them thermally stable. The layers of metal ions can slide over each other, making metals malleable and ductile; they can be drawn into wires and sheets. Metals are good conductors of electricity because the delocalized electrons can move freely, transferring energy and conducting thermal energy.

Key Points

• An octet is a set of eight. Atoms tend to gain electron configurations of the nearest noble gas for stability.
• The tendency of atoms to acquire eight-electron configurations in their valence shell when binding is called the octet rule.
• Ionic bonds are formed when one atom loses electrons and another atom gains these electrons. The force of attraction that binds oppositely charged ions is called ionic bonds.
• Ionic compounds have high melting points and conduct electricity in the molten state.
• A covalent bond is formed by the sharing of electrons between two atoms and can be single, double, or triple.
• Hydrogen bonding involves a highly electron-deficient hydrogen and a lone pair on a nearby electronegative atom.
• The adhesive action of paints and dyes is developed due to hydrogen bonding.

References for Additional Information

• Lawarie Ryan, Chemistry for You.
• lain Brand and Richard Grime, Chemistry (11-14).
• Silberg, Chemistry.
• Raymond Chang, Essential Chemistry.