Question

Both lithium and magnesium display several similar properties due to the diagonal relationship; however, the one which is incorrect, is :

• A. Both form nitrides
• B. Nitrates of both $Li$ and $Mg$ yield $NO_2$ and $O_2$ on heating
• C. Both form basic carbonates
• D. Both form soluble bicarbonates

Answer 1

The Correct Option is C

The diagonal relationship in the periodic table observes certain similarities between diagonally adjacent elements, such as lithium (Li) and magnesium (Mg). Both are known to show some similar properties due to this diagonal relationship. Let us evaluate the given options:

1. Both form nitrides: Lithium forms nitride (Li₃N) when heated in nitrogen, and magnesium also forms nitride (Mg₃N₂) under similar conditions. Thus, this statement is correct.
2. Nitrates of both Li and Mg yield NO₂ and O₂ on heating: When lithium nitrate (LiNO₃) and magnesium nitrate (Mg(NO₃)₂) are heated, they decompose to give nitrogen dioxide (NO₂) and oxygen (O₂). Therefore, this statement is correct.
3. Both form basic carbonates: Magnesium carbonate (MgCO₃) is a basic carbonate, while lithium carbonate (Li₂CO₃) is not considered a basic carbonate in the same sense because it can be decomposed easily with heat. Thus, this statement is incorrect as it applies differently to Li and Mg.
4. Both form soluble bicarbonates: It is observed that lithium does not form stable soluble bicarbonates in solution, while magnesium tends to form soluble bicarbonates when dissolved in water containing carbon dioxide. Therefore, this statement can cause confusion but is not completely accurate.

The incorrect statement, given the properties listed, is "Both form basic carbonates". This statement does not hold true in the context of the comparison between lithium and magnesium.