Question

Which one of the following is the correct increasing order of the magnitude of ionic radii of `Ce^(3+), La^(3+) , Pm^(3+)` and `Yb^(3+)` ?
A. `Yb^(3+)lt Pm^(3+) lt La^(3+) lt Ce^(3+)`
B. `Yb^(3+) ltPm^(3+) lt Ce^(3+) lt La^(3+)`
C. `Pm^(3+) ltLa^(3+) ltCe^(3+) lt Yb^(3+)`
D. `Ce^(3+) lt Yb^(3+) lt Pm^(3+) lt La^(3+)`

Answer 1

`{:(La^(3+),gt,Ce^(3+),gt,Pm^(3+),gt,Yb^(3+)),(106p m,,103p m,,98p m,,87 p m):}`
Ionic size decrease form`La^(3+)` to `Lu^(3+)` due to lanthanide contraction . Thus,
`Yb^(3+) lt Pm^(3+) lt Ce^(3+) lt La^(3+)`