Question

Which describes radioactive decay of a substance

Answer 1

Radioactive decay is the process by which an unstable atomic nucleus loses energy  by emitting radiation, such as an alpha particle, beta particle with neutrino or only a neutrino in the case of electron capture, gamma ray, or electron

Answer 2

More of the radioactivity is lost during the first half-life than in later half-lives.

Step-by-step explanation:

Radioactive phenomenon is described by decreasing exponential functions. This means that in the first stages, the most part of the energy is lost, and the remaining is release slowly in the most part of the time.

Radioactive, specifically, consists in the loss of particles from a unstable nucleus, changing from an unstable to a stable element. In the unstable period, big amount of energy is released.