The process by which a mucleus of an unstable stom loses energy by emitting particles of ionizing radiation is __ a nuclear reaction mdioactivity fusion fission a

## Step 1<br />The problem describes a process where a nucleus of an unstable atom loses energy by emitting particles of ionizing radiation. This process is known as radioactivity.<br /><br />## Step 2<br />The other options provided, such as nuclear reaction, fusion, and fission, are all related to nuclear processes. However, they do not specifically describe the process of an unstable nucleus losing energy by emitting ionizing radiation.<br /><br />## Step 3<br />A nuclear reaction is a process where two atomic nuclei or one atomic nucleus and a subatomic particle (such as a proton) collide to produce one or more atomic nuclei and subatomic particles (neutrons or protons). This does not match the description given in the problem.<br /><br />## Step 4<br />Fusion is a type of nuclear reaction where two or more atomic nuclei come together to form one or more different atomic nuclei. This also does not match the description given in the problem.<br /><br />## Step Fission is a type of nuclear reaction where a heavy nucleus splits into two or more lighter nuclei. This also does not match the description given in the problem.