The whole numbers on top of each element in the periodic table represent the atomic number.

Here's what the atomic number tells us:

* Number of protons: The atomic number is equal to the number of protons in the nucleus of an atom of that element.

* Identity of the element: Each element has a unique atomic number, so it determines what element it is.

* Number of electrons (in a neutral atom): In a neutral atom, the number of protons and electrons are equal.

Example:

* Hydrogen (H) has an atomic number of 1. This means it has 1 proton and 1 electron.

* Oxygen (O) has an atomic number of 8. This means it has 8 protons and 8 electrons.

Let me know if you have any other questions about the periodic table or atomic numbers!