Question

Given below are two statement : one is labelled as Assertion A and the other is labelled as Reason R :
Assertion A : Size of $Bk{3^{+}}$ ion is less than $Np^{3+}$ ion.
Reason R : The above is a consequence of the lanthanoid 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. Both $A$ and $R$are true and $R$ is the correct explanation of $A$
• D. $A$ is true but $R$ is false

Answer 1

Answer: (D)

Size of $_{97}Bk^{3+}$ ion is less than that of $_{93}Np^{3+}$ due to actinoid contraction. As we know that in a period from left to right ionic radius decreases and in actinide series it is due to actinoid contraction.