Question

Which of the following is not a consequence of lanthanide contraction?

(a) From La^+3 to Lu^+3, the ionic radii changes from 106 pm to 85 pm

(b) As the size of the lanthanide ions decreases the basic strength increases

(c) The basic character of oxides and hydroxides decreases with increase in atomic number

(d) The atomic radii of 4d and 5d series is similar

I had been asked this question by my school principal while I was bunking the class.

Question is taken from D and F-Block Elements topic in portion D and F-Block Elements of Chemistry – Class 12

Answer 1

Correct answer is (b) As the size of the lanthanide ions decreases the basic strength increases

For explanation: The small average decreases in the atomic size is responsible for a small decrease in electronegativity and S.O.P of lanthanides. As the size of the lanthanide ions decreases the covalent character of M—OH bond increases and hence basic strength decreases.