Question

1. (a)(i) What is the common name given to the group VII elements? (ii) Name the hydrides of the first two elements in group VII. (iii) State three chemical properties of group VII elements.
(b) Copy and complete the following table:
Particle | Number of neutrons | Number of electrons | Number of protons | Mass number
W²⁻ | 12 | ? | 8 | 24
X²⁺ | ? | 8 | ? | 16
Y | 14 | 13 | ? | 27
Z | 12 | ? | 11 | 23
(c)(i) Define each of the following processes: I. nuclear fission; II. nuclear fusion. (ii) Give one use of each process in (c)(i) above.
(d)(i) List three types of radiation that are produced during radioactivity. (ii) Arrange the radiations listed in 1(d)(i) in order of increasing: I. penetrating power; II. ionizing power.

Accepted Answer

(a)(i) Halogens. (ii) The first two elements in group VII are fluorine and chlorine; their hydrides are hydrogen fluoride and hydrogen chloride. (iii) Group VII elements: They react with metals under appropriate thermal conditions to give salts. They react with alkalis to give salts. They are good oxidizing agents.

(b) Completed table (using: for a neutral atom, protons=electrons; for a negative ion, electrons exceed protons by the magnitude of the charge; for a positive ion, electrons are fewer than protons by the magnitude of the charge; mass number = protons+neutrons):
W²⁻: protons=8, neutrons=12, electrons=10 (8+2), mass number=24
X²⁺: protons=8, electrons=8... (per the printed source, X has 8 protons and mass number 16, so neutrons=8)
Y: protons=13, neutrons=14, electrons=13, mass number=27
Z: protons=11, neutrons=12, electrons=11 (neutral), mass number=23

(c)(i) I. Nuclear fission is a process by which a large nuclide splits into two smaller nuclides of comparable masses with the release of energy and radiations. II. Nuclear fusion refers to a process by which smaller nuclides combine to give a large nuclide with the release of energy and radiation.
(ii) Nuclear fission is used in power stations for generating power. Nuclear fusion can be harnessed in the production of the hydrogen bomb.

(d)(i) Alpha particles, beta particles and gamma rays.
(ii) I. Increasing penetrating power: Alpha < beta < gamma. II. Increasing ionizing power: Gamma < beta < Alpha.

WAEC Chemistry 2013 Theory — Question 1

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