h) Metallic Crystals ​

1.46 Understand that a metal can be described as a giant structure of positive ions surrounded by a sea of delocalised electrons ​

Metal atoms are held strongly to each other by metallic bonding. In the metal lattice, the atoms lose their valence electrons and become positively charged. The valence electrons no longer belong to any metal atom and are said to be delocalised. They move freely between the metal ions like a sea of electrons. Hence, this lattice structure is described as a lattice of positive ions surrounded by a "sea of mobile electrons". We can therefore define a metallic bond as the force of attraction between positive metal ions and sea of delocalised electrons.

1.47 Explain the electrical conductivity and malleability of a metal in terms of its structure and bonding ​

Electrical conductivity ​

Metals are good conductors because of the free electron diffusion. When a metal is used in an electrical circuit, electrons entering one end of the metal cause another similar electron to displace from the other end. That's why they are very good conductors.

Malleability and ductility ​

In metallic bonding, the valence electrons do not belong to any particular metal atom. If sufficient force is applied to the metal, one layer of atom can slide over another without disrupting the metallic bonding.

As a result, metallic bonds are strong but flexible. Therefore, they can be hammered into different shapes without breaking.