Radioactivity is the spontaneous emission of radiation from the nucleus of an unstable atom. This process occurs in order for the atom to reach a more stable state.
Radioactivity occurs due to the instability of an atom's nucleus. This instability can be caused by having too many or too few neutrons, resulting in the atom being in an energetically unfavorable state.
Quantum tunnelling is a phenomenon where a particle can pass through a potential barrier, even though it does not have enough energy to overcome the barrier. In the context of radioactivity, this allows for an unstable atom to break apart and emit radiation, even though it does not have enough energy to do so based on classical physics.
Radioactivity is measured using a unit called the Becquerel (Bq), which measures the number of nuclear disintegrations per second. Another commonly used unit is the Curie (Ci), which measures the number of disintegrations per second in a larger sample of material.
Exposure to high levels of radioactivity can be harmful to living organisms as it can damage cells and DNA. It can also lead to mutations and an increased risk of developing cancer. Therefore, it is important to handle radioactive materials carefully and to limit exposure to them.