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.
Now, protons and neutrons are basically found at the atomic nucleus while electrons form the shell of the atom, moving around the nucleus. These are the basics, for further information you could go to Wikipedia (as usual) Proton, Neutron and Electron.