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

In an ionic compound A^+ X^- , the radii of A^+ and X^- ions are 1.0 p

1.	In an ionic compound A^+ X^- , the radii of A^+ and X^- ions are 1.0 pm and 2.0 pm respectively. 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 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`