The each proton present at the nucleus of an atom carry one unit positive charge and it also contributes to the mass of the nucleus. For the basic law for satisfaction of nuclear physics there remain neutron at the nucleus, which is neutral in nature. The positive charge interchange between the proton and the neutron at the nucleus.
For a neutral atom the number of electron (carries one unit negative charge) present around the nucleus must be equal to the number of protons present in the nucleus. Thus the most important point to justify the presence of proton in the nucleus among the given points is-
Protons determine the atoms' identity (type of element) and where it is located on the periodic table.
