The statements give some of the chemical properties of cobalt and its compounds. • Cobalt does not react with cold water. • Cobalt fizzes slowly with dilute hydrochloric acid. • Cobalt does not react with aqueous zinc nitrate. • Cobalt reacts with aqueous silver nitrate. • Cobalt(II) oxide reacts with magnesium to form cobalt.

1. (a)Use the information to help arrange the following metals in order of reactivity. cobalt, magnesium, silver, sodium and zinc most reactive ............................................................................................................ .............................................................................................................................. least reactive ...........................................................................................................[2]
2. (b)Construct the equation for the reaction between cobalt(II) oxide, CoO, and magnesium.[1]
3. (c)Predict what happens when cobalt(II) carbonate is heated strongly.[1]
4. (d)Cobalt has a melting point of 1495 °C. Explain, in terms of structure and bonding, why a metal such as cobalt has a high melting point. You may use a labelled diagram in your answer.[2]
5. (e)The symbol for one isotope of cobalt is ¹⁷₂₇Co. Another isotope of cobalt has a nucleon number of 59. Write its symbol.[1]