Radioactivity Revision

Gap-fill exercise

Fill in all the gaps, then press "Check" to check your answers. Use the "Hint" button to get a free letter if an answer is giving you trouble. You can also click on the "[?]" button to get a clue. Note that you will lose points if you ask for hints or clues!
Nuclear radiation occurs when the of an atom .

A small amount of Radiation is always present - from radioactive rocks (e.g. granite), radon , cosmic rays and medical or industrial sources.

Properties of radioactivity
There are three types of radioactivity Alpha a, Beta b and Gamma g.

Alpha particles are Helium , with a range of about 1 cm in air. They are stopped by . They are by a magnetic field. They are ionising.

Beta particles are electrons from the , with a range of about 1 m in air. They are stopped by 3 mm . They are deflected by a magnetic field, but in the direction to an alpha particle. They are ionising

Gamma rays are radiation, with an range. They are by lead, but not stopped altogether. In a magnetic field they carry on in a line. They have charge. They are ionising.


Only atoms decay by alpha decay. The large nucleus has too much after the alpha particle has left. It is . It loses the energy as a photon.

If a smaller atom has too many neutrons, it decays by beta decay. The atom ejects a high speed electron and an electron . This makes sure that the number is conserved.

If a smaller atom has too few neutrons, it decays by beta . The atom ejects a and an electron neutrino. The positron is an to the electron.