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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 beA. `"27 pm"^3`B. `"64 pm"^3`C. `"125 pm"^3`D. `"216 pm"^3` |
Answer» Correct Answer - D `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` |
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