Question

The ground state electron configuration of $Fe$ is_______

Answer 1

We must know about the periodic table and the electronic configuration of different elements. Electronic configuration is the distribution of electrons into orbitals. Electronic configuration follows certain rules which helps us categorize into the respective blocks. The s-block and p-block together are usually considered main-group elements, the d-block corresponds to the transition metals, and the f-block encompasses nearly all of the lanthanides and the actinides.

Complete answer:
There are certain rules which should be followed before writing the electronic configuration of elements:
Electron in an atom is characterized by a set of four quantum numbers and the maximum number of electrons that can be accommodated in a shell (energy level) is based on principal quantum number ($n$).
The maximum number of electrons that can be accommodated in a shell is calculated by the formula $2{n^2}$ where $'n'$ is the shell number. When $n = 1$, maximum number of electrons that can be accommodated are $2 \times {\left( 1 \right)^2} = 2$
The subshells into which electrons are distributed are based on the azimuthal quantum number, denoted by ‘l’. When $n = 4$ the subshells correspond to $l = 0$, $l = 1$, $l = 2$ and $l = 3$ and are named the $s,{\text{ }}p,{\text{ }}d,$ and $f$ subshells respectively.
The maximum number of electrons that can be accommodated by a subshell is given by the formula $2 \times \left( {2l + 1} \right)$ So $s,{\text{ }}p,{\text{ }}d$ and $f$ subshells can accommodate $2,6,10$ and $14$ electrons respectively.
Hence, the electron configuration of $Fe$ whose atomic number is $26$ is:
$Fe\left( {z = 26} \right) = 1{s^2}2{s^2}2{p^6}3{s^2}3{p^6}4{s^2}3{d^6}$

Note:
It must be noted that Iron $\left( {Fe} \right)$ is a transition metal that follows the Aufbau rule in filling atomic orbitals. When an atom has an atomic number of $26$, it contains 26 protons in its nucleus and $26$ electrons in its electron cloud if it is neutral.