Which of the following statements is /are correc ?
I. For a simple cubic lattice , d= a and for fcc it is `d=a//sqrt2`
II. The density of the unit cell for cubic crystals for element is `rho=(ZM)/(a^3N_Axx10^(-3)) gcm^(-3)`
III. In case of ionic compound `A^+B^-` having fcc structures as NaCl edge (a) = 2 x distance between `A^+ " and " B^-` ions .

Options

A. I and II
B. II and III
C. I and III
D. All of these

Answer

D

Explanation

For a simple cubic lattice , d=a and for fcc , `d=a//sqrt2`.
For a cubic crystal of elements , the density of the unit cell is `rho=(ZM)/(a^3N_Axx10^(-30))gcm^(-3)`
In case of ionic compounds `A^+ B^-` having fcc structures as NaCl , edge (a) = 2 x distance between `A^+ " and " B^-` ions . Hence , all the statements are correct .