Assertion. In a unit cell of NaCl, all ` Cl^(-)` ions as will they touch each other.
Reason. Radius ratio ` r_(+)//r_(-)` in NaCl is 0.414.

Answer

a

Explanation

Correct A. In a unit cell of NaCl, all ` Cl^(-)` ion touch ` Na^(+)` ion but do not touch each other.
Correct R. Actual radius ratio ` r_(Na^(+))//r_(Cl^(-))` is 0.525 and not 0.414.