Here's why:

* Electron Configuration: Potassium's electron configuration is 1s²2s²2p⁶3s²3p⁶4s¹.

* Valence Shell: The outermost shell of an atom is called the valence shell, and the electrons in that shell are called valence electrons.

* Determining Valence Electrons: In potassium's configuration, the 4s¹ electron is in the outermost shell.

Let me know if you'd like to explore the valence electrons of other elements!