Read the passage carefully and answer the following questions.
There are mainly four series of the transition metals, 3d series (Sc to Zn), 4d series (Y to Cd), 5d series (La and Hf to Hg) and 6d series which has Ac and elements from Rf to Cn. The two series of the inner transition metals; 4f (Ce to Lu) and 5f (Th to Lr) are known as lanthanoids and actinoids respectively. Their chemical properties are transitional between those of s and p-block elements. The transition metals (with the exception of Zn, Cd and Hg) are very hard and have low volatility. Their melting and boiling points are high. Transition metals have incomplete d subshell either in neutral atom or in their ions. With partly filled d orbitals these elements exhibit certain characteristic properties such as display of a variety of oxidation states, formation of coloured ions and entering into complex formation with a variety of ligands. The transition metals and their compounds are known for their catalytic activity.
In general the electronic configuration of outer orbitals of transition metals is \( (n-1)d^{1-10} ns^{1-2} \) but Pd shows an exceptional electronic configuration as......
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → \(4d^{10}5s^0\)
The outer configuration of transition elements is generally \( (n-1)d^{1-10}\,ns^{1-2} \). There are exceptions, because the (n−1)d and ns orbitals are very close in energy and half-filled and completely filled d subshells are extra stable. Cr and Cu in the 3d series are the familiar examples.
Palladium (Z = 46) has ten electrons beyond krypton. The expected configuration is \( \mathrm{[Kr]\,4d^{8}\,5s^{2}} \), but both 5s electrons go into the 4d subshell and fill it completely:
\( \displaystyle \mathrm{Pd\ (Z = 46):\ [Kr]\,4d^{10}\,5s^{0}} \)
So Pd has a completely filled 4d subshell and an empty 5s orbital, the only element whose outer s orbital is empty.
NCERT (2026-27 edition):
Electronic Configurations of the d-Block Elements – …
