New image of the Nucleus
Radioactivity --> nuclei have internal structure
First theory: protons (p) (H nucleus) + electrons
- to account for the ? and ? radiation
- protons: existence proved by Rutherford and Chadwick (1919), a new accepted elementary particle
- theoretical work shows that electrons cannot be in the nucleus!
- something else must exist, which have a mass comparable with the mass of protons (to account for the elements known relative mass)
discovery of neutrons (n) (Chadwick, 1924)
- neutrons: mass of the proton and no charge, can disintegrate in proton and electron (but not = proton+electron) , explain the mass of the elements in the periodic table + ISOTOPES (same atoms with different
mass = same number of protons, but different number of neutrons)
existence of isotopes --> non integer relative masses of the elements
protons and electrons are called nucleons