Why is a precipitate of magnesium carbonate not fomred along with the carbonates of Ba, Sr and Ca in group V?

Explanation

Magnesium requires higher concentration of `CO_(3)^(2-)` ions for its precipitation as `MgCO_(3)` which is insufficient in group V due to the presence of `NH_(4)Cl` along with `(NH_(4))_(2)CO_(3)` `NH_(4)Cl` suppresses the ionisation of `(NH_(4))_(2)CO_(3)` thereby a low concentration of `CO_(3)^(2-)` ions is made available due to common ion effect.
`NH_(4)ClhArrNH_(4)^(o+)+Cl^(ɵ)`
`(NH_(4))_(2)CO_(3)hArrunderset(("low concentration"))underset(("common ion"))(2NH_(4)^(o+))+CO_(3)^(2-)`