Question

Statement 1: The order of atomic radii of $Cu,Ag$ and $Au$ is $Cu<Ag\approx Au$
Statement 2: 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

• A. If both Statement 1 and Statement 2 are true and the statement 2 is the correct explanation o f the statement 1.
• B. If both Statement 1 and Statement 2 are true but statement 2 is not the correct explanation o f the statement 1.
• C. If Statement 1 is true but Statement 2 is false.
• D. If Statement 1 is false but Statement 2 is true

Answer 1

Answer: (B)

The atomic, radii, in general, increase down the group. The atomic radii of second series are larger than those of first transition series. In the atoms of the second transition series, the number of shells are more than those of the first transition series. As a result, the atoms of second transition series are larger than those of the elements of the first transition series. But the atomic radii of the second and third transition series are almost the same. This phenomenon is associated with the intervention of the 4f-orbitals which must be filled before the 5d series of elements begin. The filling of 4f-before 5d orbital results in a regular decrease in atomic radii called Lanthanoid contraction which essentially compensates for the expected increase in atomic size with increasing atomic number.