What 2 elements do the electrons and protons “meet up” with?

Explanation:

  Today, we know that atoms contain protons, neutrons  and electrons.  The protons have significant mass and a positive charge and are found in the nucleus of the atom.  The neutrons have mass but no charge and are also found in the nucleus.  The electrons have negative charge and very little mass and are found outside the atom's nucleus.  The weight of an atom in atomic mass units is approximately the sum of its protons and neutrons, since the electrons don't have much mass.