410 21 · NUCLEAR AND RADIOCHEMISTRY
Revision questions
21.1.In 1919, Lord Rutherford made the first artificial radio-
isotope by bombarding nitrogen atoms with alpha particles:
14
7 N4
2 He2 ?? 1
1 H
Complete the equation and identify the radioisotope he made.21.2.Tritium decays by emitting beta particles with t (^1) ⁄ 2
12.26 yr.
(i)Write an equation for the radioactive decay of tritium.
(ii)Tritium is prepared commercially by reacting lithium-6
with neutrons from a nuclear reactor. Write an equation for
the reaction.
21.3.The time for 99% of a sample of a radioisotope to decay
is given by the equation
t0.99
4.605
seconds
k
Similarly, the time for 99.9% of a sample of a radioisotope to
decay is given by
t0.9996.908seconds
k
A sample of pure polonium-210 is used in a laboratory experi-
ment. Calculate the time it takes for (a)99%,(b)99.9% of the
mass of the polonium to decay.
21.4.France generates over 70% of its electricity from nuclear
power. (The figure for the USA and for the UK is just over
20%.) Is there any ‘turning back’ for such countries that
depend so heavily upon nuclear power? Find out what would
be the advantages of adopting nuclear fusion if (and when) it
becomes available.
21.5.(i)From goverment publications, obtain a list showing
the various contributions to the background radiation to
which the population is exposed. What is the biggest source of
background radiation?
(ii)List four factors which control the degree of harm caused
by nuclear radiation to an individual.
Albert Einstein realised that through nuclear reactions even
small masses could, in principle, be converted into huge
amounts of energy. But if every gram of material contains this
tremendous energy, why did this fact go unnoticed for so long?
Einstein’s answer was simple enough: ‘So long as none of the
energy is given off externally, it cannot be observed. It is as
though a man who is fabulously rich should never spend or give
away a cent; no-one could tell how rich he was.’
Extension material to support this unit is available on our website. For more on nuclear changes and the
uses of radionuclides see Appendix 21 on the website.