The atomic core of potassium ion (K+) consists of 19 protons and 20 neutrons. Potassium has an atomic number of 19, which means it has 19 protons in its nucleus. The number of neutrons in an atom can vary, and potassium has an average of 20 neutrons in its nucleus. The combination of protons and neutrons forms the atomic core or nucleus of the potassium ion.