For the final thallium nuclide, identify the

(i) nucleon number.

(ii) proton number.

Radon-220 is a radioactive gas. It is released by rocks such as granite. In some parts of the world, houses are built from materials containing granite. Explain why it is unlikely that radon-220 will build up in sufficient quantity to be harmful in these houses.

(i) Calculate, in hour⁻¹, the decay constant of lead-212.

(ii) In a pure sample of lead-212 at one instant, 8.0 × 10⁻³ kg of the lead-212 is present. Calculate the mass of lead-212 that remains after a period of 35 hours.

(iii) A sample of pure radium begins to decay by the series shown in the table. At one instant, a mass of 8.0 × 10⁻³ kg of lead-212 is present in the sample. Suggest why, after 35 hours, there will be a greater mass of lead-212 present in the sample than the value you calculated in (h)(ii).

(i) \(\left( {\lambda  = \frac{{{\rm{In2}}}}{{{{\rm{T}}_{\frac{1}{2}}}}} = \frac{{0.693}}{{10.6}} = } \right)6.5 \times {10^{ - 2}}{\rm{ hou}}{{\rm{r}}^{ - 1}}\)

(ii) use of λ from (h)(i);
correct substitution into N = N0e−λt ;
8.0 to 8.3 × 10–4 kg;

(iii) the rate of decay/activity of polonium/radium;
is greater than the rate of decay/activity of lead;