In a solid .AB. hasving the NaCl structure, .A. atoms occupy the corners of the cubic unit cell. If the face - centrad atoms along one of the axis are removed, then the resultant stoichiometry of ther solid is

In a solid .AB. hasving the NaCl structure, .A. atoms occupy the corne

1.	In a solid .AB. hasving the NaCl structure, .A. atoms occupy the corners of the cubic unit cell. If the face - centrad atoms along one of the axis are removed, then the resultant stoichiometry of ther solid is
Answer» `AB_(2)` `A_(2)B` `A_(4)B_(3)` `A_(3)B_(4)` Solution :NaCl has a face - centered cubic close packing in which lattice points are occupied by `Cl^(-)` ions where as `Na^(+)` ions OCCUPY all octahedral holes. Here `Na^(+)` and `Cl^(-)` both have a coordination number of 6. (i) Effective number of `A^(-)` or `Cl^(-)` (normally) `= (8xx(1)/(8))+(6xx(1)/(2))=4` From corners and faces (all face centered) Effective number of `A^(-)` after removing ATOMS along one AXES. `= (8xx(1)/(8))+(4xx(1)/(2))=3` (III) Effective number of `B^(+)` or `Na^(+)` `= underset("From edge centres")((12xx(1)/(4)))+underset("From body CENTRE")(1)` = 4 `therefore` Formula is `A_(3)B_(4)`