Which of the following elements are not regarded as transition elements?
Which of the following elements are not regarded as transition elements?
$\mathrm{Zn}, \mathrm{Cd}, \mathrm{Hg}$.
$\mathrm{Cu}, \mathrm{Zn}, \mathrm{Hg}$
$\mathrm{Ag}, \mathrm{Zn}, \mathrm{Hg}$
$\mathrm{Ag}, \mathrm{Cd}, \mathrm{Hg}$
Solution
Transition elements are characterised by partially filled $(n-1) d$ subshells. $\mathrm{Zn}, \mathrm{Cd}, \mathrm{Hg}, \mathrm{Cu}$ and $\mathrm{Ag}$ all have completely filled $(n-1) d$ subshell. But $\mathrm{Zn}, \mathrm{Cd}$, and $\mathrm{Hg}$ are not considered as transition metals as in their most common oxidation state, i.e. +2 , they have $d^{10}$ configuration. Whereas $\mathrm{Cu}$ and $\mathrm{Ag}$ when exists in +2 oxidation state have $d^9$ configuration.
Electronic configuration of $\mathrm{Zn}$ is $[\mathrm{Ar}] 3 d^{10} 4 s^2$
Electronic configuration of $\mathrm{Cd}$ is $[\mathrm{Ar}] 3 d^{10} 4 s^2$
Electronic configuration of $\mathrm{Hg}$ is $[\mathrm{Ar}] 3 d^{10} 4 s^2$
Electronic configuration of $\mathrm{Cu}$ is $[\mathrm{A} r] 3 d^{10} 4 s^1$
Electronic configuration of $\mathrm{Ag}$ is $[\mathrm{Ar}] 3 d^{10} 4 s^1$