Group 2 elements are known as alkaline earth metals. They have two valence electrons and are highly reactive. The thermal stability of hydroxides and sulphates of group 2 alkaline earth metals varies down the group. The thermal stability of a compound is its ability to resist decomposition or breakdown when exposed to heat.



The thermal stability of hydroxides of group 2 alkaline earth metals increases down the group. This can be explained by the increase in the size of the metal ion down the group. As the size of the metal ion increases, the strength of the metal-oxygen bond decreases. This means that it is easier for the metal-oxygen bond to break when exposed to heat. Therefore, the hydroxide compound becomes more thermally stable down the group.



The thermal stability of sulphates of group 2 alkaline earth metals also increases down the group. This can be explained by the same reason as for hydroxides. As the size of the metal ion increases down the group, the strength of the metal-oxygen bond decreases. This means that it is easier for the metal-oxygen bond to break when exposed to heat. Therefore, the sulphate compound becomes more thermally stable down the group.



There are some exceptions to the trend of increasing thermal stability down the group. For example, magnesium hydroxide is more thermally stable than calcium hydroxide. This is because magnesium hydroxide has a smaller size and a higher charge density than calcium hydroxide. This means that the metal-oxygen bond in magnesium hydroxide is stronger than in calcium hydroxide, making magnesium hydroxide more thermally stable. Similarly, calcium sulphate is more thermally stable than strontium sulphate and barium sulphate. This is because calcium sulphate has a smaller size and a higher charge density than strontium sulphate and barium sulphate, making it more thermally stable.



In conclusion, the thermal stability of hydroxides and sulphates of group 2 alkaline earth metals increases down the group due to the increase in the size of the metal ion. However, there are exceptions to this trend, which can be explained by the size and charge density of the metal ion.