Ans. The coordination number of an atom in a crystal lattice can be determined by counting the number of nearest neighboring atoms surrounding it. These neighboring atoms are in direct contact with the central atom and are connected by chemical bonds.The coordination number can vary depending on the type of unit cell and the arrangement of atoms within it. For example, in a simple cubic unit cell, the coordination number is 6, as each atom has 6 nearest neighbors. In a body-centered cubic unit cell, the coordination number is 8, as each atom has 8 nearest neighbors.