In an ionic compound A^(+)X^(-) , the radii ofA^(+) and X^(-)ions are 1.0 pm and 2.0 pm rspecitvely . The volume of the unit cell of the crystal AX will be

In an ionic compound A^(+)X^(-) , the radii ofA^(+) and X^(-)ions are

1.	In an ionic compound A^(+)X^(-) , the radii ofA^(+) and X^(-)ions are 1.0 pm and 2.0 pm rspecitvely . The volume of the unit cell of the crystal AX will be
Answer» `27 "pm"^(3)` ` 64 "pm"^(3)` ` 125 "pm"^(3)` ` 216 "pm"^(3)` Solution :` (r_(A^+))/(r_(X^(-))) = 1/2 = 0.5 `,As it lies in the range that of NaCl. 0.414 - 0.732 , AX has octahedral structure like that of NaCl. Hence,edge LENGTH `= (a) =2 (r_(+) + r_(-))`= 2 (1 + 2) pm = 6 pm Volume of the unit cell = ` a^(3) = ( 6 "pm")^(3) = 216 "pm"^(3)`