(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 pr...

(a)(i) The Group VII elements are commonly called the halogens.

(a)(ii) The hydrides of the first two elements (fluorine and chlorine) are hydrogen fluoride, \( HF \) and hydrogen chloride, \( HCl \).

(a)(iii) Three chemical properties of Group VII elements

• They are strong oxidizing agents (their oxidizing power decreases down the group).
• They react with metals to form salts (metal halides), for example \( 2Na + Cl_2 \rightarrow 2NaCl \).
• They react with hydrogen to form hydrogen halides, and a higher halogen displaces a lower one from its salt solution.

(b) Completed table

Using mass number \( = \) protons \( + \) neutrons, and for an ion the electrons \( = \) protons \( - \) (positive charge):

• \( W^{2+} \): neutrons 12, mass 24, so protons \( = 24 - 12 = 12 \); electrons \( = 12 - 2 = 10 \).
• \( X^{2+} \): protons 8, mass 16, so neutrons \( = 16 - 8 = 8 \); electrons \( = 8 - 2 = 6 \).
• \( Y \): electrons 13 (neutral, so protons 13), mass 27, so neutrons \( = 27 - 13 = 14 \).
• \( Z \): electrons 11 (neutral, so protons 11), neutrons 12, so mass number \( = 11 + 12 = 23 \).

(c)(i) I. Nuclear fission: the splitting of a heavy nucleus into two lighter nuclei of comparable mass, with the release of a large amount of energy. II. Nuclear fusion: the combination of two light nuclei to form a heavier nucleus, with the release of a large amount of energy.

(c)(ii) Fission is used in nuclear power stations to generate electricity (and in the atomic bomb). Fusion is the source of the energy of the sun and stars (and of the hydrogen bomb).

(d)(i) The three radiations are alpha, beta and gamma radiation.

(d)(ii) I. Increasing penetrating power: alpha \( < \) beta \( < \) gamma. II. Increasing ionizing power: gamma \( < \) beta \( < \) alpha.