The atom and radioactivity


The Atom, the Nucleus and Radioactivity (all questions were taken from exam papers)

  1. What is the structure of an alpha particle?

  2. The diagram shows a simplified arrangement of an experiment carried out early in the 20th century to investigate the structure of the atom

  1. Name the scientist who carried out this experiment.

  2. Describe what was observed in this experiment.

  3. Why was it necessary to carry out this experiment in a vacuum?

  4. What conclusion did the scientist form about the structure of the atom?

  1. Describe the Bohr model of the atom.

  2. How many neutrons are in a 14C nucleus?

  1. What is an isotope?

  2. What is radioactivity?

  3. Give an application of radioactivity.

  4. Radioactivity causes ionisation in materials. What is ionisation?

  5. Describe an experiment to demonstrate the ionising effect of radioactivity.

  6. What is radioactive decay?

  1. 14C decays to 14N. Write an equation to represent this nuclear reaction.

  2. Write a nuclear equation to represent the decay of carbon-14 by beta emission.

  1. Apart from “carbon dating”, give two other uses of radioactive isotopes.

  1. Explain the term half-life.

  2. Cobalt−60 is a radioactive isotope with a half-life of 5.26 years and emits beta particles.

(i) Write an equation to represent the decay of cobalt−60.

(ii) Calculate the decay constant of cobalt−60.

(iii) Calculate the rate of decay of a sample of cobalt−60 when it has 2.5 × 1021 atoms.

  1. A neutral pion is unstable with a decay constant of 2.5 × 1012 s–1.
    What is the half-life of a neutral pion?

  1. The activity of a radioactive isotope decays to one sixteenth of its original value after 36 years.

What is the half-life of the isotope?

  1. An ancient wooden cup from an archaeological site has an activity of 2.1 Bq. The corresponding activity for newly cut wood is 8.4 Bq.

  1. If the half-life of carbon-14 is 5730 years, estimate the age of the cup.

  2. How much of a 14C sample remains after 11 460 years?

  3. Calculate the decay constant of 14C.

  4. Why does the 12C in dead tissue remain “undisturbed”?

  1. Name an instrument used to measure the activity of a sample.

  1. What is the principle of operation of this instrument?