Historically the dining room is furnished with a rather large dining table and a number of dining chairs; the most common shape is generally rectangular with two armed end chairs and an even number of un-armed side chairs along the long sides.
Protons and neutrons do not have the same mass. Their masses are quite close, but they are noticeably different. For some purposes it is okay to equate the neutron and proton mass, but it's just an approximation.Also, neutrons decay into a proton, an electron and an antineutrino.rotons and neutrons do not have the same mass. Their masses are quite close, but they are noticeably different. For some purposes it is okay to equate the neutron and proton mass, but it's just an approximation.
Isotopes differ from one another in the number of neutrons they possess. Because of their differing number of neutrons, isotopes also differ in their mass numbers, the total number of protons and neutrons. Neutrons have no charge, but they do contribute mass to an atom, about the same mass a proton contributes. This difference in the number of neutrons imparts different physical properties to the isotopes. Many of the elements found in nature comprise a mixture of different isotopes.