The number of nearest neighbours and next nearest neighbours of an `Na^(o+)` ion in a crystal of `NaCl` are, respectively,

Options

A. `6Na^(o+), 12Cl^(Θ)`
B. `6Cl^Θ, and 12Na^(o+)`
C. `12Cl^(Θ), 12Na^(o+)`
D. `6Cl^(Θ), 6Na^(o+)`

Answer

B

Explanation

`Na^(o+)` lies in `Ovs` formed by `Cl^(ɵ)` (`Na^(o+)` touches six `Cl^(ɵ)` ions)

`Na^(o+)` and `Cl^(ɵ)` are not shown touching in the figure.
Each atom shown is present at the face centre of each cube.
[Distance between `Na^(o+)` and `Cl^(ɵ) = a/2`

Try to visulize two cubes exactly above these two cubes.
Eaches atoms shown is present at the edge centre and body centre of each cube.
Distance between two neasest a`Na^(o+) = (a)/(sqrt(2))`
(i). Thus, the number of neaset neighbours of `Na^(o+)` ion `= 6 Cl^(ɵ)` ions
ii. The number of next nearest neighbour of `Na^(o+)` ions `= 12 Na^(o+)` ions