91Ó°ÊÓ

Considering the contribution of atoms in the unit cell, the atoms in the corner of the cube contribute 1/8^th to one cubic cell, the body-centered atom contributes a whole atom for that cell and the face-centered atom contributes half for the unit cell.

Polonium, Po has metal atoms in the corner of the cell, thus contributing,

$\mathbf{8}\mathbf{×}\left(\frac{1}{8}\right)\mathbf{=}\mathbf{1}$

Therefore, a total of one metal atom is present in the cell.

Manganese, Mn has metal atoms in the corner as well as in the body center of the cell, thus contributing,

$\mathbf{8}\mathbf{×}\left(\frac{1}{8}\right)\mathbf{+}\mathbf{1}\mathbf{=}\mathbf{2}$

Therefore, a total of two metal atoms are present in the cell.

Silver, Ag has metal atoms in the corner as well as in the six-face center of the cell, thus contributing,

$\mathbf{8}\mathbf{×}\left(\frac{1}{8}\right)\mathbf{+}\mathbf{6}\mathbf{×}\left(\frac{1}{2}\right)\mathbf{=}\mathbf{4}$

Therefore, a total of four metal atoms are present in the cell.