This chart shows four atoms, labeled W, X, Y, and Z. These
atoms can combine with each other to form molecules.
Which atoms could join together to form a molecule of an
element?
Atom
W
X
Element
oxygen
hydrogen
carbon
oxygen
Wand X
X and Y
W and Z
Y and Z

The proton has a positive charge while the neutron has no charge they both make up the nucleus of the atom while the elections have a negative charge and surround the nucleus of the atom. the protons and electrons are used to calculate the atom's mass whereas the neutrons don't affect the mass