3. ATOMIC STRUCTURE 3.1 Electrons,

3. ATOMIC STRUCTURE

3.1 Electrons, Protons and Neutrons

Their relative charges and relative masses.

3.2 The Nucleus of the Atom

(a) Isotopes and mass number.

(b) Radioactivity (a treatment of proton: neutron ratio is not required).

(i) The nature of a- and b- particles and of g- rays.
Radioactive decay as a random phenomenon.
Differences in penetrating ability should be mentioned, form the
point of view of radiation protection, but a treatment of the detailed
physical evidence establishing the nature of a- and b- particles and
g- rays is not intended.

(ii) Half-life, as a measure of the relative stability of the nucleus.
Calculations on half-life and use of the exponential decay law.

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(iii) The effect of a- and b- particle emission on mass number and
atomic number.

(iv) The balancing of nuclear equations.

e.g. 1
3
H fi 2
3
He + 1
0
e

1
1
H + 3
6
Li fi 2
3
He + 2
4
He

(c) The common isotopes of uranium, 235U and 238U.

The neutron-induced fission of 235U resulting in

(i) the release of large quantities of energy (given by E = mc2),
(ii) the production of further neutrons – leading to the possibility of
chain reaction,
(iii) the formation of lighter radioactive fission fragments.

(d) Fusion of light elements as a source of energy.

Reference should be made to the fact that the source of energy in the sun is a
series of fusion reactions.