Write a brief note on the electronic configurations of the transition elements.

(N/A) The general electronic configuration of $d$-block elements is $(n-1)d^{1-10}ns^{1-2}$. The $(n-1)$ stands for the inner $d$-orbitals,which may have one to ten electrons,and the outermost $ns$-orbital,which may have one to two electrons.
Certain exceptions are observed in the electronic configurations of $d$-block elements due to the very small energy difference between $(n-1)d$ and $ns$ orbitals.
For example,$Cr$ $(3d^5 4s^1)$ exhibits stability due to the half-filled $d$-subshell,and $Cu$ $(3d^{10} 4s^1)$ exhibits stability due to the fully-filled $d$-subshell.
The electronic configurations of transition elements are summarized in the following table:

Series	Elements	Configuration
$3d$	$Sc$ to $Zn$	$(n-1)d^{1-10}ns^{1-2}$
$4d$	$Y$ to $Cd$	$(n-1)d^{1-10}ns^{0-2}$
$5d$	$La$ to $Hg$	$(n-1)d^{1-10}ns^{1-2}$
$6d$	$Ac$ to $Cn$	$(n-1)d^{1-10}ns^{1-2}$