Final answer:
A potassium ion (K+) has 19 protons and 18 electrons, as it has lost one electron from its neutral atomic state which has an equal number of protons and electrons.
Step-by-step explanation:
The ion described in the question is a potassium ion (K+). To determine the number of protons and electrons in this ion, we can refer to potassium's atomic number, which is 19. This number tells us that a neutral potassium atom contains 19 protons and 19 electrons. Since a potassium cation has a single positive charge (K+), it indicates that this ion has lost one electron compared to the neutral atom.
Therefore, a K+ ion still has 19 protons, as the number of protons does not change, but it only has 18 electrons because one electron has been removed to achieve the positive charge.