Question

What is the electronic configuration of potassium?
A. $1s^{2}2s^{2}2p^{6}3s^{2}3p^6$
B. $[Ar]4s^1$
C. $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^1$
D. $3s^{2}4s^{2}4p^3$

Answer 1

Hint: Electronic configuration tells us about the distribution of electrons of an atom or molecule in atomic or molecular orbitals. Electronic configuration was first discovered through the Bohr model of the atom which generally describes shells and subshells.

Complete answer:
The electron distribution in electronic configuration firstly states the maximum number of electrons in their shells like s subshell acquire at most 2 electrons, p subshell have 6, d have 10 electrons, f subshell have 14 electrons and g subshell acquire 18 electrons in its orbit. The distribution of electron is based on the three principles called Aufbau principle, Pauli Exclusion Principle and Hund’s rule which can be described as follows:
1. Aufbau principle: It states that electrons fill lowest atomic orbitals first after their completion and it moves towards higher level atomic orbitals. The subshell ordering according to this rule is given by: $1s,2s,2p,3s,3p,4s,3d,4p,5s,4d,5p,6s,4f,5d,6p,7s,5f,6d,7p,8s,5g......$
2. Pauli Exclusion Principle: It states that no electrons in an atom are allowed to have the same set of quantum numbers.
3. Hund’s rule: This rule states that before the double occupation of any orbital it firstly singly occupied.
Potassium is the chemical element represented by $$K$$ and atomic number of potassium is 19. So its electronic configuration is based on above three rules and given as $$1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^1$$ and can also be written as $[Ar]4s^1$ where $$Ar$$ represents argon having atomic number 18 and have electronic configuration$1s^{2}2s^{2}2p^{6}3s^{2}3p^6$.

Hence option B is the correct answer.

Note:
Potassium is generally kept in the category of metals but it has an exceptional case that it can be easily cut with a knife. It is an essential component for the nutrition of plants and soils, also used in medicines to treat and prevent low body potassium.