How do I keep each new subject of my document appearing on top of the page even if it gets pushed to the next page as new texts are added to the previous sections.

For instance if I am writing about Protons I want Protons to be on page 1 and say Neutrons to be on page two, but if the text for the Protons fills up two pages then the neutrons text would be pushed to page 3.

I would like to know how do I do that? Thank you!