Hi

Two characteristics of the d-block (transition) elements are that they exhibit variable oxidation states and form coloured compounds. (i) State two possible oxidation states for iron and explain these in terms of electron arrangements.

+2 and +3/Fe 2+ and Fe 3+ ; both s electrons are lost giving Fe 2+ and one more d electron is also lost to form Fe 3+ ;

Define the term ligand. Cu 2+ (aq) reacts with ammonia to form the complex ion [Cu(NH3)4] 2+ . Explain this reaction in terms of an acid-base theory, and outline the bonding in the complex ion formed between Cu 2+ and NH3.

ligand: a molecule or ion that can bond to a (central) metal ion (to form a complex); NH3: Lewis base and Cu 2+ : Lewis acid (need both for mark); each NH3/ligand donates an electron pair (to Cu 2+ ); forming coordinate covalent/dative covalent bond;

By reference to the structure and bonding in the compounds NaCl and SiCl4 (i) state and explain the differences in conductivity in the liquid state.

NaCl conducts and SiCl4 does not; NaCl ionic and SiCl4 covalent; ions can move in liquid (in NaCl)/OWTTE; 3 (ii) NaCl pH = 7; salt of strong acid and strong base/Na + and Cl - not hydrolysed; SiCl4 pH = 0 to 3; HCl is formed/strong acid formed;