Question

Assertion: $\text{Zn}$, $\text{Cd}$, and $\text{Hg}$ are not regarded as transition elements.
Reason: The electronic configurations of $\text{Zn}$, $\text{Cd}$, and $\text{Hg}$ are represented by the general formula $\left( \text{n-1} \right){{\text{d}}^{\text{10}}}\text{n}{{\text{s}}^{\text{2}}}$
A) Both assertion and reason are correct and reason is the correct explanation for assertion.
B) Both assertion and reason are correct but the reason is not the correct explanation for assertion.
C) Assertion is correct but the reason is incorrect.
D) Both assertion and reason are incorrect.

Answer 1

Transition elements are those that are represented by the general formula $\left( \text{n-1} \right){{\text{d}}^{\text{1 to }}}^{\text{10}}\text{n}{{\text{s}}^{\text{1 to 2}}}$and they are called so because they exhibit characteristics that range from group 2 to group 13.

Complete step by step solution:
The transition elements are those elements in the periodic table, which have valence electrons in the “d”- orbital, these can be the 3d, 4d, 5d, 6d, etc. orbitals. These elements are called the “Transition Elements'' as they show a transition in their properties as the electrons are added up to the d-orbitals.
$\text{Zn}$, $\text{Cd}$, and $\text{Hg}$ are not regarded as transition elements because their d-subshell is totally full-filled and thus they do not show much tendency to accept electrons in their 3d orbitals. So they are in their ground state as well as their most common oxidation state $\left( {+2} \right)$. As they do not show much transition in their properties, they are not regarded as transitional elements. So Assertion is correct and the reason is the correct explanation of the assertion.

Hence, the correct answer is option A.

Note:
The transition metals have similar properties that are quite different from the groups in the periodic table.
Some of the most notable properties of the transition metals are:
They are good conductors of heat and electricity, they are malleable and ductile, they have high melting and boiling points, they are hard and have high tensile strength, they have high densities, they form different coloured salts, they are reactive in nature but not as much as the alkali metals, they possess variable valences.