Diagonal Relationship Of Lithium And Magnesium

Diagonal relationship of lithium with magnesium

The main points of similarity :

1) Both have almost similar electronegativities.

2) Both Li and Mg are quite hard. They are harder and lighter than other elements in their respective groups.

3) Both LiOH and Mg(OH)₂ are weak bases.

4) Both form ionic nitrides when heated in atmosphere of Nitrogen.

6 Li + N₂ ——–> 2 Li₃N

3 Mg + N₂ ——–> 2 Mg₃N₂

5) The hydroxides of both lithium and magnesium decompose upon heating.

2 LiOH —–> Li₂O + H₂O

Mg(OH)₂ —-> MgO + H₂O

6) Both lithium and magnesium combine with oxygen to form monooxide while other members of their respective groups form peroxide and superoxide.

4 Li + O₂ —–> 2 Li₂O

2 Mg + O₂ —–> 2 MgO

The Li₂O and MgO thus formed do not combine with excess O₂ to form peroxide and superoxide.

7) The carbonates of these metals decompose on heating to the corresponding oxides with the evolution of carbon dioxide.

Li₂CO₃ ——-> Li₂O + CO₂

MgCO₃ ———–> MgO + CO₂

8) Both Lithium and magnesium do not form solid bicarbonates.

9) Both Lithium and magnesium nitrate decompose on heating producing nitrogen dioxide.

4 LiNO₃ ——> 2 Li₂O + 4 NO₂ + O₂

2 Mg(NO₃)₂ ———-> MgO + 4 NO₂ + O₂

10) The hydroxides ,carbonate, oxalates, phosphates and fluorides of both Lithium and magnesium are sparingly soluble in water.

11)Because of the covalent character , LiCl and MgCl₂ are soluble in ethanol.

12) Both Lithium perchlorate and magnesium perchlorate are highly soluble in ethanol.

13) LiCl and MgCl₂ are deliquescent and crystallise from aqueous solution as hydrate LiCl·2 H₂O and MgCl₂ ·6 H₂O.