Two isotopes of carbon are carbon-12 and carbon-14. One of these isotopes, carbon-14, undergoes radioactive decay.

1. (a)Describe what is meant by radioactive decay. ............................................................................................................................................................................. [2][2]
2. (b)Carbon-12 has a proton number (atomic number) of 6 and a nucleon number (mass number) of 12. Complete Table 7.1 for a neutral atom of each of these two isotopes. [Table 7.1] carbon-12 carbon-14 number of protons 6 number of neutrons number of electrons [2][2]
3. (c)(i)A sample of carbon-14 is contained in a thin aluminium container of thickness 0.2 mm. Radiation from the sample is detected outside the container. When the thickness of the aluminium is increased to 6 mm, no radiation from the sample is detected outside the container. State the type of radiation which is stopped by increasing the thickness of the aluminium. ............................................................................................................................................................................. [1][1]
4. (c)(ii)Explain how you know that the sample does not emit one other type of radiation. ............................................................................................................................................................................. ............................................................................................................................................................................. ............................................................................................................................................................................. [2][2]