Question

A solid AB has Zn S-type structure. If the edge
length of the unit cell is 400 pm and the radius of
B-ion is 0.130 nm then the radius of A+ ion is
(1) 35.8 pm
(2) 43.2 pm
(3) 60.5 pm
(4) 53.2 pm
Which of the following is correct?
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Answer 1

Solution :

a=2(r++r−)a=2(r++r−)

500=2(80+r−)500=2(80+r−)

500=160+r−500=160+r−

500−160=2r−500−160=2r−

340=2r−340=2r−

34023402=r−=r−

r−=170r−=170

∴∴ the radius of anion =170pm