Question

The electronic configuration of potassium is :
A) $1s^2,2s^2,2p^6,3s^2,3p^3,4s^2,3d^2$
B) $1s^2,2s^2,2p^6,3s^2,3p^5,4s^2$
C) $1s^2,2s^2,2p^6,3s^2,3p^6,3d^1$
D) $1s^2,2s^2,2p^6,3s^2,3p^6,4s^1$

Answer 1

Hint: Basically, The electronic configuration of an element describes how electrons are allotted in its atomic orbitals. The orbitals are filled according to the Aufbau’s rule which states that lower energy orbitals will be filled first.

Complete answer:
In atomic physics and the quantum chemistry branch, the electronic configuration is the total distribution of atom electrons or molecules in an outer atomic or molecular orbitals or shells, this is beneficial for describing the important chemical bonds that hold the atoms together bound.
This configuration specifies the total number of electrons in the atom. The number of electrons in the particular atom is identical to the atomic number of that element.
Electron configurations of atoms follow a rule wherein all electron-containing atomic subshells are positioned in a sequence. However, the usual notation frequently yields lengthy electron configurations (mainly for elements having an especially huge atomic number). In such cases, an abbreviated or condensed notation can be used in place of the standard notation. In the abbreviated notation, the series of absolutely filled subshells that correspond to the configuration of a noble gas is replaced with the different symbol of that noble gas in the square brackets.
The number of electrons in the atom is the atomic number of the element, electronic configuration in the orbitals of the atom are filled in the order 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s.
Potassium (K) have atomic number 19 and configuration is $1s^2,2s^2,2p^6,3s^2,3p^6,4s^1$

So the correct answer is option D.

Note: The electronic configuration given in subshell notation indicates how many electrons are in the subshell of each shell. Maximum subshells can accommodate two electrons and they must have opposite spins and this is in accordance with Pauli’s Exclusion Principle.