What is the electron configuration of lithium, oxygen, nitrogen and potassium?

The electron configuration of an element describes the distribution of electrons in its atomic orbitals. Here are the electron configurations for lithium (Li), oxygen (O), nitrogen (N), and potassium (K):

Lithium (Li): Atomic number 3
Electron configuration: 1s² 2s¹

Oxygen (O): Atomic number 8
Electron configuration: 1s² 2s² 2p⁴

Nitrogen (N): Atomic number 7
Electron configuration: 1s² 2s² 2p³

Potassium (K): Atomic number 19
Electron configuration: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹

In electron configurations, the numbers and letters represent the following:

The first number represents the principal quantum number (n) and denotes the energy level or shell of the electron.
The letter(s) represent the subshell (s, p, d, f) where the electron resides.
The superscript number indicates the number of electrons in that subshell.
For example, in the electron configuration 1s² 2s¹ for lithium, "1s²" means there are 2 electrons in the 1s subshell, and "2s¹" means there is 1 electron in the 2s subshell.