Question

In a simple cubic lattice, the coordination number is:
(A) $4$
(B) $5$
(C) $6$
(D) $8$

Answer 1

Hint : Analyse the structural diagrams of simple cubic lattice from solid state and then find the number of atoms adjacent neighbouring a single atom. Simple cubic lattice has overall one atom combining its all the contributing atoms.

Complete step by step solution
First let us see what coordination number is. Coordination numbers come into picture when we discuss the solid state of matter.
When we discuss crystals of solid there is a central atom and surrounding atoms. The number of atoms or ions which surround the central atom is called coordination number of that crystal. It is also called ligancy of the compound.
Now let us analyze the structure of a simple cubic lattice. A simple cubic lattice is the simplest structure for a lattice arrangement. The structure of simple cubic lattice can be imagined to be a square placed on top of another square. The number of lattice points in simple cubic lattice is eight. It has eight atoms present at each corner of the cube. An atom in the cubic lattice is in touch with four other atoms in the plane and one-one atom above and below the plane each. So the coordination number of a simple cubic lattice is $6$ .
So option C is the correct answer.

Note
Number of atoms per unit cell and coordination number of a compound are two different things. For example in BCC there are a total of eight atoms in a unit cell. So the number of atoms per unit cell of BCC is $1/8$ .
For reference the coordination number of different structures are:
Coordination number of BCC is $8$
Coordination number of FCC is $12$
Coordination number of CCP is $12$
Coordination number of HCP is $12$ .