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Rutherford's model of the atom

firing alpha particles at a piece of gold foil

most alpha particles passed straight through

small number repelled and bounced back

atom is mainly empty space

repulsion between alpha particle + positively charged nucleus

nucleus is very small

Bohr model

electrostatic force of attraction between oppositely charged sub-atomic particles prevents electron from leaving the atom

neutrons are not electrically charged= stability of nuclei

Protons would repel eachother if there were no neutrons

Definitions

Atomic number: the number of protons in the nucleus

Mass number: the number of protons plus the number of neutrons in an atom