This question is about the transition elements and how they compare with the Group I metals. Fig. 12.1 shows part of the Periodic Table. The block of elemen...

This is a broad question comparing transition elements with Group I metals across position, properties, oxidation states, catalysis, colour and uses. Take each part in turn.

(a) Block T is the transition elements (the d-block / transition metals) [1], lying between Group II and Group III [1].

(b) Any three transition elements, for example iron, copper and nickel (chromium, manganese, cobalt, zinc or vanadium also accepted) [3].

(c) Any four differences: transition metals have higher density, higher melting point, are harder / stronger, form coloured compounds, show variable oxidation states, act as catalysts, and are less reactive than Group I metals [4].

(d) Copper(I) oxide is Cu₂O [1] and copper(II) oxide is CuO [1]. Two copper(I) ions are needed to balance one oxide ion, but only one copper(II) ion is needed.

(e) Variable oxidation state means the atoms can lose different numbers of their outer electrons [1], forming ions or compounds with more than one oxidation number such as Cu⁺ and Cu²⁺ [1].

(f) The ammonia synthesis is reversible:

N₂(g) + 3H₂(g) ⇌ 2NH₃(g) [2]

One condition, for example about 450 °C, about 200 atm, or an iron catalyst [1].

(g) A catalyst speeds up the forward and backward reactions equally, so the position of equilibrium is unchanged [1]; it is still valuable because equilibrium is reached faster, or a lower temperature can be used, saving time and energy [1].

(h) Aqueous copper(II) sulfate is blue [1] and iron(III) hydroxide is red-brown [1].

(i) Any two uses other than as catalysts, for example stainless steel for cutlery or construction and copper for electrical wiring or pipes (brass for fittings, or chromium/nickel for plating, also accepted) [2].