Assertion : The order of atomic radii of `Cu, Ag` and `Au` is `Cu lt Ag ~~ Au`.
Reason : The atomic radii of `4d` series elements are larger than those of `3d` series elements but generally the radii of `4d` and `5d` series elements are almost identical.

Options

A. Statement-1 is true , Statement-2 is true and Statement-2 is correct explanation for Statement-1
B. Statement-1 is true, Statement-2 is True and Statement-2 is Not correct explanation for statement-1
C. Statement-1 is true, Statement-2 is False
D. Statement-1 is False, Statement-2 is True

Answer

B

Explanation

The atomic radii, in general, increase down the group. The atomic radii of second series are larger than those of first transition saries. In the atoms of the second transition series , the number of shells are more than those of the Ist transition series . As a result, the atom IInd transition series are larger than those of the elements of the first transition series . But the atomi radii of the second and third transition series are almost the same . This phenomenon is associated with with intervention of the `4f` orbitals which must be filled before the `5d` series of elements begin. The filling of `4f` orbitals results in regular decrease in atomic size with increasing atomic number .