A neutral atom has a nucleus containing protons and neutrons, with orbiting electrons. Let p p\,p represent the number of protons, n n\,n represent the number of neutrons, and e e\,e represent the number of electrons. Which relationship must be correct for this atom?
e=ne = ne=n
e=pe = pe=p
n=pn = pn=p
e=p+ne = p + ne=p+n
284 exam-style questions on CIE IGCSE Physics 5.1 The nuclear model of the atom, covering 5.1.1a Structure of the atom and ions, 5.1.1b Alpha-particle scattering, 5.1.2a Composition of the nucleus and isotopes, 5.1.2b Proton number, nucleon number and nuclide notation, and 5.1.2c Nuclear fission and nuclear fusion. Each one has a worked solution and a mark scheme showing where the marks go.