A compound consisting of the monovalent ions A^+ ,B^- crystallizes in the body-centred cubic lattice. (i)What is the formula of the compound ? (ii)If one of A^+ ions from the corner is replaced by a monovalent ions C^+, what would be the simplest formula of the resulting compound ?

A compound consisting of the monovalent ions A^+ ,B^- crystallizes in

1.	A compound consisting of the monovalent ions A^+ ,B^- crystallizes in the body-centred cubic lattice. (i)What is the formula of the compound ? (ii)If one of A^+ ions from the corner is replaced by a monovalent ions C^+, what would be the simplest formula of the resulting compound ?
Answer» Solution :(i)Contribution of `A^+` ions present at the CORNERS towards unit CELL =`8xx1/8=1` Contribution of `B^-` ion present at the body-centre=1 `therefore` Ratio of `A^+ :B^-` =1:1 .Hence , the formula is AB. (ii)`A^+` ions at the corners =7. Hence, their contribution towards unit cell=`7/8` `C^+` ion at ONE CORNER contributes =`1/8` `B^-` ion at the body centre has contribution =1 Hence, ratio of A:B:C=`7/8:1/8:1=7:1:8 therefore ` Formula will be `A_7BC_8`