In the given crystal structure what should be the cation X which replaces `Na^(+)` to create a cation vacancy ?

Options

A. `Sr^(2+)`
B. `K^(+)`
C. `Li^(+)`
D. `Br^(-)`

Answer

A

Explanation

Each `Sr^(2r+)` in the NaCl replaces two `Na^(+)` ions. It occupies the site the of one ion and the other remain vacant creating a cation vacancy.