Francium-224, ⁶⁴₂₉Cu and ⁹⁸₄₃Tc are stable because they have a stable neutron/proton ratio.
⁶⁰₂₈Ni and Platinum-196 are radioactive because they have an odd number of protons and neutrons.

⁶⁴₂₉Cu and ⁹⁸₄₃Tc are radioactive because they have an odd number of protons and neutrons.
⁶⁰ Francium-224, ₂₈Ni and Platinum-196 are stable because they have a stable neutron/proton ratio.

Francium-224 is radioactive because it has a high atomic number.
⁶⁴₂₉Cu and ⁹⁸₄₃Tc are stable because they have a stable neutron/proton ratio.
⁶⁰₂₈Ni and Platinum-196 are radioactive because they have an odd number of protons and neutrons.

Francium-224 is radioactive because it has a high atomic number.
⁶⁴₂₉Cu and ⁹⁸₄₃Tc are radioactive because they have an odd number of protons and neutrons.
⁶⁰₂₈Ni and Platinum-196 are stable because they have a stable neutron/proton ratio.