What is the electronic configuration of potassium (K)?

Explanation

Potassium has 19 electrons that fill energy levels in order. The first shell holds 2 electrons, the second holds 8, the third holds 8, and the last electron goes in the fourth shell.

Writing this out gives: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹. The numbers show which shell, the letters show the orbital type, and the superscripts show how many electrons.

Potassium has one electron in its outermost 4s orbital, making it highly reactive. This single outer electron is easily lost, which is why potassium forms positive ions readily.