The thermal stability increases down the group.

BeCO$_3$ is more thermally stable than MgCO$_3$ due to the high polarizing power of Be$^{2+}$

BaCO$_3$ decomposes at a much higher temperature than MgCO$_3$.

The decomposition of these carbonates yields the corresponding metal oxide and CO$_2$.

Fused salt electrolysis

Self reduction

Aqueous solution electrolysis

Thermite reduction

Fused salt electrolysis

Self reduction

Aqueous solution electrolysis

Thermite reduction

Fireworks

Military signals

Photographic flash bulbs

All of the above

Bauxite

Malachite

Carnallite

Haematite

Carnallite

Dolomite

Calamine

Sea water

${\rm{MgC}}{{\rm{O}}_3}$

${\rm{Mg}}{\left( {{\rm{N}}{{\rm{O}}_2}} \right)_2}$

${\rm{Mg}}{\left( {{\rm{N}}{{\rm{O}}_3}} \right)_2}$

${\rm{M}}{{\rm{g}}_3}{{\rm{N}}_2}$

Magnesium

Calcium

Strontium

Barium

Fireworks

Military signals

Photographic flash bulbs

All of the above

Carnallite

Dolomite

Calamine

Sea water

Magnesium acts as an oxidizing agent

Magnesium has 2 electrons in the outermost orbit

Magnesium acts as a reducing agent and removes oxygen from ${\rm{C}}{{\rm{O}}_2}$

None of the above