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

CsClcrystallises in body-centred cubic lattice. If 'a' is its edge len

1.	CsClcrystallises in body-centred cubic lattice. If 'a' is its edge length then which of the following expressions is correct ?
Answer» `r_(Cs^+)+r_(Cl^-)=sqrt3a` `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 CHARGED ions touch each other ALONG the body diagonal `THEREFORE` Body diagonal, AE=`2r_(Cs^+)+ 2r_(Cl^-)` But body diagonal =`sqrt3a` (From right angled `triangleCDE`, CE=`sqrt(a^2+a^2)=sqrt2a` From right angled `TRIANGLE ACE` , `AE=sqrt(AC^2+CE^2)=sqrt(a^2+2a^2)=sqrt(3a^2)=sqrt3a`) `therefore 2(r_(Cs^+)+r_(Cl^-))=sqrt3a` or `r_(Cs^+) +r_(Cl^(-))=sqrt3/2a`