Three members of the halogens are: ^35.5₁₇ Cl, ⁸⁰₃₅Br and ¹²⁷₅₃I.

a. (i) Write down the electronic structure of an atom of chlorine.

(ii) Why is the relative atomic mass of chlorine not a whole number?

(iii) How many protons are there in an atom of bromine?

(iv) How many neutrons are there in an atom of iodine?

(v) State and account for the order of reactivity of these elements.

b. When potassium is allowed to burn in a gas jar of chlorine, in a fume cupboard, clouds of white smoke are produced.

(i) Why is this reaction carried out in a fume cupboard?

(ii) What does the white smoke consist of?

(iii) Write a word and balanced chemical equation for this reaction.

(iv) Describe what you would expect to see when potassium is allowed to burn safely in a gas jar of bromine vapour. Write a word and balanced chemical equation for this reaction.