Question

Discuss the trend of the following: Thermal stability of carbonates of Group 2 elements.

Answer 1

On heating, metal carbonates breakdown, releasing carbon dioxide from the long-term carbon cycle into the short-term carbon cycle and leaving behind a metal oxide. Calcination is named after calx, the Latin word for quicklime or calcium oxide (CaO), which is made by roasting limestone in a lime kiln.

Complete answer:
The metal oxide and carbon dioxide gas are produced by heat breakdown of all carbonates in this category. The phrase "thermal decomposition" refers to the process of breaking down a substance by heating it.
All Group 2 carbonates and the oxides that arise are white solids. This decomposition is described as follows if "X" represents any of the elements:
$XC{O_3}(s) \to XO(s) + C{O_2}(g)$
The carbonates take greater heat to breakdown as they progress through the group. Down the group, the carbonates grow more thermally stable.
A large amount of charge is packed into a tiny volume of space in a small ${2^ + }$ ion. In other words, it has a large charge density and has a significant distorting impact on any nearby negative ions. Because the same charge is dispersed over a wider amount of space in a larger ${2^ + }$ ion, its charge density is lower, causing less distortion to neighbouring negative ions. When the carbonate is heated, the carbon dioxide escapes and the metal oxide remains. The quantity of heating required is determined by the degree of polarisation of the ion. Less heat is required for more polarisation. The higher the charge density of the positive ion, the greater the influence it will have on the carbonate ion.
The carbonate ions near the positive ions have less of an effect as the positive ions go bigger along the group. For the carbon dioxide to exit the metal oxide, more heat is required. In other words, as the group progresses, the carbonates grow more thermally stable.
$BeC{O_3}\; < {\text{ }}MgC{O_3}\; < {\text{ }}CaC{O_3}\; < {\text{ }}SrC{O_3}\; < {\text{ }}BaC{O_3}$ .

Note:
Although the carbonate ions of most metals are insoluble in water, the bicarbonate salts are not. The balance between carbonate, bicarbonate, carbon dioxide, and carbonic acid in solution is continuously shifting due to variations in temperature and pressure. In the presence of metal ions and insoluble carbonates, insoluble compounds develop. Hard water causes scale accumulation within pipes, which may be explained in this way.