Fill in the electronic configurations for the free ions below. • $\text{Co}^{2+}$ $[\text{Ar}]$ … • $\text{Co}^{3+}$ $[\text{Ar}]$ …
Both $\text{Co}^{2+}$ and $\text{Co}^{3+}$ form complexes with $\text{edta}^{4-}$. Using the table data, predict what happens, if anything, when separate aqueous solutions of $\text{Co}^{3+}$ and $[\text{Co(edta)}]^{-}$ are left in air. • aqueous solution of $\text{Co}^{3+}$ • aqueous solution of $[\text{Co(edta)}]^{-}$
Hydrated cobalt(II) nitrate, $\text{Co(NO}_3)_2\cdot6\text{H}_2\text{O}$, is a red solid and behaves like hydrated magnesium nitrate, $\text{Mg(NO}_3)_2\cdot6\text{H}_2\text{O}$, on heating. Describe in detail what you would observe when crystals of $\text{Co(NO}_3)_2\cdot6\text{H}_2\text{O}$ are heated in a boiling tube, first gently and then more strongly.
Explain why the thermal stability of the Group 2 nitrates increases down the group.