## College Physics (4th Edition)

We can write the symbol for this isotope of potassium: $^{40}_{19}K$
The upper number is the total number of nucleons (neutrons and protons), while the bottom number is the number of protons. The element potassium has 19 protons in the nucleus and potassium has the chemical symbol $K$. We can write the symbol for this isotope of potassium: $^{40}_{19}K$