Question

What is the electronic configuration of bromine?

Answer 1

Hint: Atomic number of bromine is $35$, by using $spdf$ subshell electronic configuration; as s block can fit $2$ electrons, p can fit maximum $6$, d can fit maximum $10$ and f can fit maximum $14$ electrons. The first shell has only an s, then the second shell is $2s,2p$ then third shell $3s,3p,3d$ then fourth shell $4s,4p,4d,4f$ and so on.

Complete step by step answer:
Since, bromine has atomic number $35$, follow the order to fill the subshell
$
  1s \\
  2s2p \\
  3s3p3d \\
  4s4p4d4f \\
  5s5p5d5f \\
  6s6p6d \\
  7s7p \\
 $
After filling up the electron in each row, the next row again starts with $s$, the first shell will be $1{s^2}$ then $2{s^2}$after that $2{p^6}$. Now out of $35$,$10$ electrons are filled more $25$ electron are remaining, so again $3{s^2},3{p^6},3{d^{10}}$, only $7$ electrons are remaining. Now the maximum number of electrons in $p$ shell can be $6$. So the last box of $p$ shell will remain empty and $4{s^2},4{p^5}$.
Writing it all together $1{s^2}2{s^2}2{p^6}3{s^2}3{p^6}3{d^{10}}4{s^2}4{p^5}$
In short, we can write it as $[Ar]4{s^2}3{d^{10}}4{p^5}$

 Note: Each element has different electronic configuration. The orbitals are basically mathematical functions that describe the wave nature of the electron. All four $s,p,d,f$ have different shapes. $s$ and $p$ are most common orbitals in biological and organic chemistry.