6.0 STRUCTURE AND BONDING

Why does salt shatter like a crystal but a metal wire can be bent? Why is diamond the hardest natural substance while graphite is soft and slippery? The answers lie in the way atoms are held together – the bonds between them and the structures they form. This chapter explores the three main types of chemical bonding (ionic, covalent, and metallic) and explains how bonding and structure determine the properties of materials. This is the key to understanding why different substances behave the way they do.

6.1 IONIC BONDING (TRANSFER OF ELECTRONS)

Ionic bonding occurs between a metal and a non-metal. It involves the complete transfer of one or more electrons from the metal atom to the non-metal atom. This creates ions: the metal becomes a positively charged cation, and the non-metal becomes a negatively charged anion. The oppositely charged ions then attract each other strongly – this electrostatic attraction is the ionic bond.

6.1.1 How Ionic Bonds Form

• Metal atoms have few electrons in their outer shell (usually 1, 2, or 3) and tend to lose them to achieve a stable full outer shell (like a noble gas).
• Non-metal atoms have many electrons in their outer shell (usually 5, 6, or 7) and tend to gain electrons to achieve a stable full outer shell.
• The loss and gain happen simultaneously. The metal atom donates electron(s) to the non-metal atom.

Example: Sodium chloride (NaCl)

• Sodium (