The most common oxidation states of cobalt are +2 and +3. Complete the electronic configurations of the following free ions. • Co2+ [Ar] • Co³+ [Ar]

1. (a)The most common oxidation states of cobalt are +2 and +3. Complete the electronic configurations of the following free ions. • Co2+ [Ar] • Co³+ [Ar][1]
2. (b)Co2+ and Co³+ both form complexes with edta⁴-. half-equation E°/V Co3+ + e- ⇌ Co2+ +1.82 O2 + 4H+ + 4e¯ ⇌ 2H₂O +1.23 [Co(edta)] + e¯ ⇌ [Co(edta)]2- +0.38 Co2+ + 2e- ⇌ Co -0.28 Use the data in the table to predict what happens, if anything, when separate aqueous solutions of Co³+ and [Co(edta)] are left to stand in the air. aqueous solution of Co³+ aqueous solution of [Co(edta)]-[3]
3. (c)Hydrated cobalt(II) nitrate, Co(NO3)2•6H2O, is a red solid that behaves like hydrated magnesium nitrate, Mg(NO3)2•6H₂O, when heated. Describe in detail what you would expect to observe when crystals of Co(NO3)2•6H2O are heated in a boiling tube, gently at first and then more strongly.[2]
4. (d)Explain why the thermal stability of the Group 2 nitrates increases down the group.[2]

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