Each question is worth 3 points. Isotopes have similar chemical properties and the same nuclear composition. Isotopes have different chemical properties and different nuclear composition.
Isotopes have different chemical properties, but generally the same nuclear composition.
Isotopes generally have similar chemical properties, but often different nuclear composition. Rn-222 decays by emission of an alpha particle. In 1932, James Chadwick bombarded beryllium-9 with alpha particles. One product was a neutron. This led to the direct experimental verification of the existence of neutrons.