1: 4.The process by which an atomic NUCLEUS of an unstable atom loses mass and energy by emitting IONIZING particles.A material containing unstable nuclei is considered radioactive.Three of the most common types of decay are alpha decay, BETA decay, and gamma decay, all of which INVOLVE emitting one or more particles or photons. \(N_1 = {{N^o} \over 2^6}\)\(N_1 = {{N_0} \over 2^\frac{6}{2}}\)\(N_1 ={{N_0} \over 2^3}\)\({N_1\over N_2} = {8}\)\(A ={λN} \)\(A = {{0.693} \over T}\)\({A_1\over A_2}= {{N_1T_2} \over N_2T_1}={1:4}\)