Question

5th period element with no electrons in 5th orbit is:
A. Pd
B. Pt
C. Ni
D. Zn

Answer 1

Hint: The 5th period composed of 18 elements that begins with rubidium and ends with xenon. Some 5th period elements are rubidium, yttrium, zirconium, niobium, molybdenum, technetium, ruthenium, rhodium, palladium, silver, cadmium xenon and so on.

Complete step by step answer:
The given problem can be easily solved by having slight knowledge about the 5th period elements. So, from the given options, platinum (Pt) belongs to the 6th period, zinc (Zn) and nickel (Ni) both belong to the 4th period and only palladium (Pd) belongs to the 5th period.
The atomic number (Z) of Pd is 46 having electronic configuration but experimentally the e electronic configuration of Pd is: . We know that the completely filled orbitals are more stable than partially filled orbitals, which is a driving force.
The levels are said to be degenerate at high energy levels, which means the energies are very close and electrons can easily jump from one orbital to the other. In the case of palladium (Pd), the energies of 5s and 4d orbitals are very close to each other. Therefore, to get the stable electronic configuration electrons from 5s orbital jumps to the 4d orbital.
Hence, the 5th period element with no electrons in 5th orbit is palladium (Pd).
The given problem can be easily solved by having slight knowledge about the 5th period elements. So, from the given options, platinum (Pt) belongs to the 6th period, zinc (Zn) and nickel (Ni) both belong to the 4th period and only palladium (Pd) belongs to the 5th period.
The atomic number (Z) of Pd is 46 having electronic configuration but experimentally the e electronic configuration of Pd is: . We know that the completely filled orbitals are more stable than partially filled orbitals, which is a driving force.
The levels are said to be degenerate at high energy levels, which means the energies are very close and electrons can easily jump from one orbital to the other. In the case of palladium (Pd), the energies of 5s and 4d orbitals are very close to each other. Therefore, to get the stable electronic configuration electrons from 5s orbital jumps to the 4d orbital.
Hence, the 5th period element with no electrons in 5th orbit is palladium (Pd).
So, the correct answer is “Option A”.

Note:
We need to memorize that the half-filled and the fully filled orbitals are more stable than partially filled orbitals. The reason for the stability is symmetry as well as exchange energy.