It is now known that protons and neutrons are themselves build out of elementary units called quarks. The up quark (u) has charge #+(2e)/3# and down quark (d) has charge #-e/3#. What can be the composition of proton and neutron?

1 Answer
May 8, 2018

#"Proton = uud"#
#"Neutron = udd"#

Explanation:

A proton has a charge of #+e# and given #"u"=+(2e)/3# and #"d"=-e/3#, we can find that #(+(2e)/3)+(+(2e)/3)+(-e/3)=+(3e)/3=+e#, and so a proton has #"uud"#.

Meanwhile a neutron has a charge of #0#, and #(+(2e)/3)+(-e/3)+(-e/3)=(+(2e)/3)+(-(2e)/3)=0#, so a neutron has #"udd"#.