12.2 Nuclear Physics

Iodine-131  has a half-life of 8.02 days.

Calculate the decay constant of .

The initial activity of the sample of Iodine−131 is 6.5 × 10⁴ Bq.

Iodine−131 decays through a number of decay modes. Two of these are decay of 606 keV and gamma emission of 364 keV. The product of the  decay is . 

Ernest Rutherford was able to deduce a relationship for the size of the nucleus using the Rutherford scattering experiment shown below:

A radioisotope has a nuclear radius of 7.41 fm

A beam of high-energy neutrons is directed at the nucleus and a pattern is formed on a detector screen.

The neutrons are accelerated to a speed of 2.88 × 10⁸ m s⁻¹.

The decay constant of the isotope is 9.72 × 10⁻¹⁰ yr⁻¹. The mass of a sample of this isotope is 600 g.

A nucleus of sodium−24 decays into a stable nucleus of magnesium−24. It decays by β^– emission followed by the emission of γ-radiation as the magnesium−24 nucleus de-excites into its ground state.

The sodium−24 nucleus can decay to one of three excited states of the magnesium−24 nucleus. This is shown in the diagram below:

The energies of the excited states are shown relative to the ground state.

The excited magnesium nucleus de-excites through production of gamma radiation of discrete wavelengths.

The graph shows the activity of a sample of sodium−24 with time.

The detector in this experiment measures 4% of the activity from the sample.

Americium-241 has a half-life of 432 years. A small sample is held in a school for use in experiments.

The teacher uses a Geiger-Müller counter to measure the count rate at close range. The relationship between activity and count rate is a ratio of 6:1. Over 5 minutes, the count is 13 600. 

Americium−241 decays through a series of decays to uranium-233.

The energies from each decay path are recorded. 

The beta decay of protactinium−233 to uranium−233 has a half−life of 27 days. A sample of protactinium has an activity of 3879 Bq.