13028 15 (a) Thallium is a metallic element that exhibits typical metallic properties. It has a relatively high melting point and is a good electrical conductor. (i) Explain why thallium has a relatively high melting point. [2] (ii) Explain why thallium conducts electricity. [2] (b) The electron configuration of thallium can be represented as [Xe] 4f14 5d10 6s2 6p1 . (i) Explain why thallium is described as a p-block element. [1] (ii) State the period and group of the Periodic Table in which thallium is found. period: group: [2] (iii) Thallium forms the ions Tl+ and Tl3+. Using the representation above, write the electron configuration of these ions. Tl+:    [Xe] Tl3+: [Xe]                             [2] 13028 [Turn over (c) Thallium(I) sulfate was used in rat poison. It was prepared by the reaction of thallium with sulfuric acid. Write the equation for the reaction of thallium with sulfuric acid. [2] (d) Thallium(III) oxide is a black solid which decomposes into thallium(I) oxide and oxygen at 800 °C according to the equation: Tl2O3(s)  →  Tl2O(s)  +  O2(g) Calculate the loss in mass when 1.72 g of thallium(III) oxide are heated to constant mass. Give your answer to 3 significant figures. [3]