CBSE Class 12-science Answered
The body-centered cubic unit cell has atoms at each of the eight corners of a cube plus one atom in the center of the cube. Corners will always be 1/8 and 1 in the center.(show graphics of bcc & fcc and show counting of each component)
Corners 8 x 1/8 = 1
Body center 1x1=1
therefore total 2 atoms per unit cell.
The face centered cubic structure has atoms located at each of the corners and the centers of all the cubic face Eight eighths from corners atoms and six halves of the face atoms.
Corner 8x 1/8 = 1
Face 6x 1/2 = 3 therefore total 4. As iron crystallizes as FCC it will have 4 atoms and gold crystallizes as BCC it will have 2 atoms. Number of atoms are more in iron than gold.