(N/A) The distribution of electrons into the orbitals of an atom is called its electronic configuration.
Method-$1$: (Electronic configuration by orbital notation): The subshell is represented by its respective letter symbol,and the number of electrons present in the subshell is depicted as a superscript. The subshells belonging to different shells are differentiated by writing the principal quantum number before the respective subshell. General configuration is represented as $n_{1}s^{a}n_{2}p^{b}n_{3}d^{c}$.
Example: Electronic configurations expressed by orbital notation for $B(Z=5), C(Z=6), N(Z=7), O(Z=8), F(Z=9)$ and $Ne(Z=10)$ are as follows:
| Atom | Electronic configuration by orbital notation |
| $B(Z=5)$ | $1s^{2}2s^{2}2p^{1}$ |
| $C(Z=6)$ | $1s^{2}2s^{2}2p^{2}$ |
| $N(Z=7)$ | $1s^{2}2s^{2}2p^{3}$ |
| $O(Z=8)$ | $1s^{2}2s^{2}2p^{4}$ |
| $F(Z=9)$ | $1s^{2}2s^{2}2p^{5}$ |
| $Ne(Z=10)$ | $1s^{2}2s^{2}2p^{6}$ |
Method-$2$: (Electronic configuration by orbital diagram): Each orbital of the subshell is represented by a box as shown below:
$s$-orbital: [ ]
$p$-subshell: [ ][ ][ ]
$d$-subshell: [ ][ ][ ][ ][ ]
The electron is represented by an arrow $(\uparrow)$ for a positive $(+\frac{1}{2})$ spin or an arrow $(\downarrow)$ for a negative $(-\frac{1}{2})$ spin.