Question

'AB' has rock salt structure. Radius of
cation is 100pm. If the radius of anion is
1.6 times that of cation then the edge
length of unit cell of AB will be
(A) 520 pm
(B) 260 pm
(C) 160 pm
(D) 320 pm​

Answer 1

Answer:if AB is a rock salt structure

Then, r+=100

r-=1.6×100

Now, edge length is

2(r++r-)=a

2(100+1.6×100)=a

a=200(2.6)

a=26×20

a=520pm

Explanation:

Hope it helps you

Answer 2

Given:

Radius of cation = 100pm

Radius of anion = 1.6 times

To Find:

Length of unit cell AB

Solution:

In Rock salt structure the relationship between the radius of anion, radius of cation and the edge length is -

R+ + R- = a/2

Where R+ is radius of cation and R- is radius of anion

Therefore,

R+ = 100

R- = 1.6 × 100  = 160

Edge length is

2(r++r-) = a

2( 100 + 160 ) =a

a = 2 ( 260 )

a = 2 × 260

a = 520

Answer : Length of unit cell AB is 520pm