Metals in general have they chemical property of reacting with an acid. Zinc reacts with hydrochloric acid to produce hydrogen gas. This is a chemical property. Chemical change results in one or more substances of entirely different composition from the original substances.
After a radioactive atom decays, it is the same element that it
was before with no measurable change in mass. the decay that is present is
gamma decay because gamma decay has photons which has no mass unlike alpha and
beta decay.