Rutherford picture of atom from scattering expt (1910)
		• Atom is mostly empty space with positive charge (protons) concentrated in a dense central core called the nucleus.  (Neutrons are also in the nucleus--Chadwick experimental evidence in 1932 for neutron) • Positive core  of atom deflects a particles strongly. • ‘It was almost as incredible as if you fired a 15- inch shell at a piece of tissue and it came back and hit you.”