Question

Give the total score of the correct statements of the following.

	Statements	Score
a.	In an antifluorite structure, cations are present in all tetrahedral voids.	$1$
b.	If the radius of cation is $0.35$ pm and that of anion is $0.95$ pm, then the co-ordination number of the crystal is $4$.	$2$
c.	An atom or ion is transfered from a lattice site to an interstitial position in Frenkel defect.	$3$
d.	The density of a crystal always decreases in point defects.	$4$

Answer 1

Statements (a), (b) and (c) are correct. So, the total score $=1+2+3=6$
Statement (a, b) are factual.
In an antifluorite structure, cations are present in all tetrahedral voids.
If the radius of cation is $0.35$ pm and that of anion is $0.95$ pm, then the coordination number of the crystal is $4$.
$\frac{r_{\oplus }}{r_{⊝}}=\frac{0.35}{0.95}=0.368$
The radius ratio lies in the range of $0.225-0.414$, which corresponds to tetrahedral void and the coordination number of tetrahedral void $=4$
An atom or ion is transferred from a lattice site to an interstitial position in Frenkel defect.
The density of a crystal may or may not decrease in point defects.