Question

Given below are two statements: One is labelled as Assertion A and the other is labelled as Reason R.
Assertion A: Size of $B{k}^{3+}$ ion is less than $N{p}^{3+}$ ion.
Reason R: The above is a consequence of the lanthanide contraction.
In the light of the above statements, choose the correct answer from the options given below.

• A. A is false but R is true
• B. Both A and R are true but R is not the correct explanation of A
• C. A is true but R is false
• D. Both A and R are true and R is the correct explanation of A

Answer 1

The correct option is C A is true but R is false

${}_{93}N{p}^{3+}$ and ${}_{97}B{k}^{3+}$ belong to actinide series. As atomic number increase, ionic size decreases.
It is due to actinoid contraction.