Lithium and magnesium

  Some of the chemical properties of Li that make it diagonally related to Mg rather than vertically related to the other alkali metals are summarized overleaf.

• Lithium readily combines with N₂ to give the nitride, Li₃N; Mg reacts with N₂ to give Mg₃N₂.
• Lithium combines with O₂ to give the oxide Li₂O rather than a peroxide or superoxide) Mg forms MgO. The peroxides of both metals can be formed by reacting LiOH or Mg(OH)₂ with H₂O₂.
• Lithium and magnesium carbonates decompose readily on heating to give Li₂O and CO₂, and MgO and CO₂ respectively; down the group, the carbonates of the group 1 metals become increasingly stable with respect thermal decomposition.
• Lithium and magnesium nitrates decompose on heating whereas NaNO3 and the later alkali metal nitrates decompose according to equation 11.35.

• The Li and Mg^2‏+ ions are more strongly hydrated in aqueous solution than are the ions of the later group 1 and 2 metals.
• LiF and MgF₂ are sparingly soluble in water; the later group 1 fluorides are soluble.
• LiOH is much less soluble in water than the other alkali metal hydroxides; Mg(OH)₂ is sparingly soluble.