How do you find protons and electrons on a periodic table?

The atomic number (number at the top) is the amount of protons and the amount of electrons. So if an element has an atomic number of 5, you know that it has 5 protons and 5 electrons. The atomic mass (number at the bottom) is the amount of protons and neutrons added together.

Explanation:

it means there are 3 atoms of oxygen