What is inside the nucleus?
1910 the atom was thought to consist of a massive nucleus
orbited by electrons, but measurements of atomic mass
indicated that all nuclei must contain integer numbers
of some other particle. What were these particles
inside the nucleus?
of these particles was the proton. The proton was discovered
during investigations of positive rays, and can be produced
by ionising hydrogen. Hydrogen is the lightest type
of atom, consisting of a single proton and a single
electron. Ionisation separates the electron from the
atom, so only the proton remains.
more massive nuclei contained only protons their charge
would be much higher than measurements suggested. With
the exception of hydrogen all atoms have a higher mass
number than charge number. Rutherford thought that the
nucleus consisted of protons and 'neutral doublets'
formed from closely bound protons and electrons. This
could explain both the mass and the charge that had
been measured for different nuclei.