Which statement is true?: - beta radioactivity is not found until ~Z = 82 (Pb)

- beta radioactivity tends to occur in isotopes with a lower neutron to proton ratio

- fission and alpha radioactivity are more common in heavier elements (Z > 82)

- fission isn't found in heavier elements (only Z < 40).

answer: enthalpy

explanation:

for a exothermic reaction, the energy is released i.e. the energy of the products is lower than the energy of the reactants.

= enthaply

= energy of products

= energy of reactants

as , thus comes out to be negative. negative value of enthalpy shows that the reaction is exothermic.