Question

5th period element with no electrons in 5th orbit is:

• A. Pd
• B. Pt
• C. Ni
• D. Zn

Answer 1

The correct option is A Pd

The atomic number of Palladium is 46:$1s^2,2s^2,2p^6,3s^2,3p^6,4s^2,3d^{10},4p^6,5s^2,4d^8$

But the experiment has shown that the electron configuration of Palladium is:

$1s^2,2s^2,2p^6,3s^2,3p^6,4s^2,3d^{10},4p^6,5s^0,4d^{10}$

Reasons :

Completely filled d orbitals are more stable than partially filled ones.

At higher energy levels,the levels are said to be degenerated which means that they have very close energies and then electrons can jump from one orbital to another very easily.

5th period element with no electrons in 5th orbit is $Pd$

Hence option A is correct.