This question was attempted by majority of the candidates and the performance was good. The question covers topic from the periodic table, atomic structure and radioactivity. In part (a), majority of the candidates were able to answer questions on the group VII elements naming their hydrides and stating their chemical properties.
In part (b), the properties of the fundamental particles of atom were well attempted by majority of the candidates but that of the ions were missed out by some candidates. In part (c), majority of the candidates could not properly define nuclear fission and fusion and give one use of each.
In part (d), the candidates were able to list the types of radiation produced during radioactivity. However, some candidates could not arrange the radiation in order of increasing penetrating and ionizing power.
The expected answers include:
(a) (i) Halogens
(ii) Hydrogen fluoride
(iii) - high electron affinity/strong oxidizing agents/electron acceptor
- highly electronegative;
- react with hydrogen to form acid;
- form salts with metals;
- react with alkalis to form salts;
- react with water to for acids;
- displacementof lower halogens from their acids/salts;
- react with hydrocarbon to form alkyl halides.
Particles Number of neutrons Number of electrons Number of Protons Mass Number
W2+ 12 10 12 24
X2- 8 10 8 16
Y 14 13 13 27
Z 12 11 11 23
(c)(i) I. Nuclear fission – splitting of a heavy nucleus into two smaller nuclei of similar
mass with the release of large amount of energy and radiations.
II. Nuclear fusion – combination of smaller nuclei to form a large nucleus with the
release of large amount of energy and radiation.
(ii) I. Used to generate electricity/nuclear bomb/production of new elements/production of
II. Used to produce nuclear weapon/atomic bomb/production of new elements/production radioisotopes.
(d) (i) alpha, beta, gamma
a , ß, ?
(ii) I. a < ß
increasing penetrating power
II. ?<ß < a
increasing ionizing power