Question

Give the correct order of initials T (true) or F (False) for following statements:
I. In an anti-fluorite structure, anions form FCC lattice and cations occupy all tetrahedral voids.
II. If the radius of cations and anions are $0.2\mathring{A}$ and $0.95\mathring{A}$, then co-ordination number of cation in the crystal is $4$.
III. An ion is transferred from a lattice site to an interstitial position in Frenkel defect.
IV. Density of crystal always increases due to substitutional impurity defect.

• A. TFFF
• B. FTTF
• C. TFFT
• D. TFTF

Answer 1

The correct option is D TFTF

I. In an anti-flourite structure, anions form FCC lattice and cations occupy all tetrahedral voids.

II. Ratio of radius $=\frac{0.2}{0.95}=0.21$ which lies between $0.155-0.225$ and so, it has co-ordination number of $3$.

III. Frenkel defect is a defect which is created when an ion leaves its appropriate site in the lattice and occupies an interstitial site. A hole or vacancy is thus produced in the lattice.

IV. The density of crystal may increase/decrease due to substitutional impurity defect.

Hence, the correct option is $\text{D}$