Question

A solid XY crystallizes in NaCl type structure (X is cation). Someatoms are removed such that crystal remain neutral. The possiblecase is​

Answer 1

Answer:

According to the structure of NaCl  

Here,  

′

A  

′

  will occupy 8 corners of  cubic unit cell which will contribute  

8

1

​  

 each to the cube

therefore 8×  

8

1

​  

=1

and 6 face centered atoms will contribute  

2

1

​  

 to the cube

Hence 6×  

2

1

​  

=3

Therefore total contribution of atom'A' is 3+1=4

Now B occupies octahedral voids (NaCl structure)  which contributes 1/4

therefore 1+12×  

4

1

​  

=4

So the formula is A is-

A  

4

​  

B  

4

​  

orAB

Now  we are removing all  face centered atoms along one axis-

so the number of atoms removed from cube are 2

so contribution from 'A' remains 8×  

8

1

​  

(corneratoms)+4×  

2

1

​  

(facecenteredatoms)=3

so the resultant becomesA  

3

​  

B  

4

​