# In a sample of the element potassium, what does each atom contain?

Jun 10, 2017

An atom of potassium contains PRECISELY 19 protons, 19 massive, positively charged $\text{nucular particles}$. And thus $Z , \text{ the atomic number,} = 19$, which specifies the element to be potassium. And because this was a NEUTRAL potassium atom, there were also 19 electrons, 19 extranuclear particles of negligible mass that are conceived to whizz about the nuclear core.......
The presence of 20 or 21 or 19 neutrons within the nucleus gives rise to the phenomenon of $\text{isotopes}$, which are the same atom (i.e. because $Z = 19$ still, but have a slightly different mass.