Question

Write the electronic configuration of $K$ and $Cl$.

Answer 1

Electronic configuration is the arrangement of electrons in the energy levels around an atomic nucleus in orbit. Electronic configuration helps us to determine the group and period the element belongs to, the valency and valence electrons of the element.

Complete answer:
Let us first consider the element Potassium $K$.
The atomic number of potassium is $19$. We know it is an Alkali metal and the number of electrons in its outermost shell is $1$. It belongs to the fourth period.
According to Neil Bohr there are four subshells to the nucleus. They are divided into $K,L,M,N$. Keeping in mind the octet rule, the number of electrons in the respective subshells are $K = 2$, $L = 8$, $M = 8$, $N = 1$.
The electronic configuration of $K$ is $2,8,8,1$.
Let us now consider the element Chlorine $Cl$.
The atomic number of Chlorine is $17$. It is known as a Halogen element and the number of electrons in its outermost shell is $7$. It belongs to the third period.
According to Neil Bohr there are four subshells to the nucleus. They are divided into $K,L,M,N$. Keeping in mind the octet rule, the number of electrons in the respective subshells are $K = 2$, $L = 8$, $M = 7$.
The electronic configuration of $Cl$ is $2,8,7$.

Note:
Both the elements, Potassium $K$ and Chlorine $Cl$ have the same valency $1$. Potassium $K$ in order to attain the electronic configuration of the nearest noble gas Argon $Ar$ readily donates an electron while Chlorine $Cl$ readily accepts an electron to attain electronic configuration of the nearest noble gas Argon $Ar$.