The Nuclear Constituent or Nucleons

The nucleus of atoms consist of protons and neutrons as its constituent, they are also called the nucleons. They are located at the nucleus of atoms and bounded together by strong inter-nucleon force.   

The nucleons both protons and neutrons are made up of quarks, protons and neutrons are not elementary particles of atoms, there are quarks . The protons consist of three quarks; two up quarks and one down quark likewise the neutron consist of three quarks, one up quark and two down quarks.  The three quarks in the either of the nucleons are held together by nuclear force called strong interaction , this force is being mediated by the exchange of quantum particles called gluons.

The protons has a positive electronic charge of +1 same magnitude as the charge on the electron (1.66 x 10^-19C) the reason for proton having  a positive charge of  +1e is because it has two up quarks each with a electronic charge of +2/3 and one down quark with electronic charge of -1/3, by  adding the sum of all charge posses by the three quarks in proton, (+2/3 +2/3 -1/3)= (4-1)/3 =1, therefore protons has the electrical charge of +e, likewise the neutron has  no electronic charge, this is why it is electrically neutral, hence the name neutron, the neutron has three quarks , two down quarks each with electronic charge of -1/3 and one up quark with electronic charge of +2/3,  by adding up the total charge in the neutron as follow (-1/3 + -1/3 +2/3) = 0/3 =0, therefore proton has zero electronic charge.

 the proton has the mass of 1.6 x10^-27kg which is equivalent to 938.27MeV/c², this mass can also be expressed in atomic mass unit as 1.007825u  while the neutron has the  a mass of  1.6749 x10^-27kg  which is equivalent to 939.37mev/c² , the neutron mass can expressed in atomic mass unit as 1.008665u , the neutron is 0.1% heavier than the proton.

Proton are independently stable on their own, with a very long half life that made them practically stable, where as  neutrons are independently unstable, they need to be bind to other particle to remain stable,  though both proton and neutron can be made stable or unstable depending on the nucleus they found them same.

In the nucleus of an atom only the protons and neutrons are found independently, though other particles can be born out of them but they do not exist independently. Two or more nuclides with same number of proton but different nucleon number or nuclei mass are said to be isotopes, isotopes tend to have same chemical properties but different nuclear properties e.g uranium -235 and uranium -238.

Two or more nuclides with same atomic mass but different proton number are said to be isobars e.g helium -6 and lithium-6, they tend to have same mass but different chemical properties. Two or more nuclides with same number of proton but different atomic mass are called isotones, examples of isotones are phosphorus - 31 and silicon -32.