CsCl crystallises in body - centred cubic lattice. If 'a' is its edge length the which of the following expressions is correct ?

CsCl crystallises in body - centred cubic lattice. If 'a' is its edge

1.	CsCl crystallises in body - centred cubic lattice. If 'a' is its edge length the which of the following expressions is correct ?
Answer» ` r_(Cs+)+ r_(Cl^(-)) = sqrt3 a ` `r_(Cs^(+)) + r_(Cl^(-)) = 3A ` ` r_(Cs^(+) + r_(Cl^(-)) = (3a)/2` `r_(Cs^(+)) + r_(Cl^(-))= sqrt3/2 a ` SOLUTION :In body-centred cubic (BCC) , oppositely chargedions touch each other along the body diagonal . Body diagonal , ` AE = 2r_(Cs^(+)) + 2r_(Cl^(-))` But body diagonal = ` SQRT 3a ` ( From right angled` DeltaCDE, CE =sqrt(a^(2) +a^(2))= sqrt2a ` From right angled ` Delta ACE` ` AE = sqrt( AC^(2)+ CE^(2)) = sqrt(a^(2) + 2a^(2)) = sqrt(3a^(2)) = sqrt3 a `) `2(r_(Cs^(+)) +r_(Cl^(-)) = sqrt3 a or r_(Cs) + r_(Cl^(-)) = sqrt3/2 a `