Given below are two statements: 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 lanthanide contraction.
In the light of the above statements, choose the correct answer from the options given below:

Assertion A states that the size of $$Bk^{3+}$$ (Berkelium) ion is less than $$Np^{3+}$$ (Neptunium) ion. In the actinide series, $$Np$$ (atomic number 93) comes before $$Bk$$ (atomic number 97). As we move across the actinide series from left to right, the ionic radii decrease due to the poor shielding effect of $$5f$$ electrons, similar to the lanthanide contraction but in the actinide series. Since $$Bk$$ is further along the actinide series than $$Np$$, $$Bk^{3+}$$ is indeed smaller than $$Np^{3+}$$. So Assertion A is true.

Reason R states that this is a consequence of the lanthanide contraction. This is incorrect. The lanthanide contraction refers to the steady decrease in ionic radii across the lanthanide series ($$4f$$ elements from La to Lu). The decrease in size from $$Np^{3+}$$ to $$Bk^{3+}$$ is a consequence of the actinide contraction (poor shielding by $$5f$$ electrons), not the lanthanide contraction. While the phenomenon is analogous, it is technically the actinide contraction, not the lanthanide contraction.

Therefore, A is true but R is false. The correct answer is Option (3).