Atoms and Molecules

The relative atomic mass of $$ Ne$$ is $$20.$$ Its relative molecular mass is:
Represent each of the following:
i)  a proton 'p',              ii)  an electron 'e',
iii) a neutron 'n' in terms of its symbols.
According to Dalton, atoms combine in a fixed ratio to form ___________.
Name the following with reference to the elements of the modern periodic table.
Define the following terms.