Question

Maximum thermal stability is shown by:
(A) $MgC{O_3}$
(B) $CaC{O_3}$
(C) $SrC{O_3}$
(D) $BaC{O_3}$

Answer 1

A molecule is formed when atoms combine with each other in definite ratio. This molecule is more stable than individual atoms. A molecule is said to be more stable when it does not break easily.

Complete step by step answer:
When we go down the group in the periodic table the size of the atoms gradually increases. Metals are mostly present in s group. In S group two sub groups are divided this is alkali metals and alkaline earth metal. Alkali metal is the $1st$ group of periodic table and alkaline earth metal group is the $2nd$ group of periodic table. Metals are electropositive in nature, it means metals having capacity to lose electrons.
When we go down the group the electropositive nature of metals increases gradually because the size of metal increases when we move down the group.
Thermal stability may be defined as if a molecule requires more heat to decompose then it means that molecule is highly thermal stable. When we go down the group the thermal stability is also increased. Also the carbonates of metals thermal stability increases down the group.
So $SrC{O_3}$ is more thermal stable as compared to other carbonates of their metal in the same group. It means $SrC{O_3}$ requires more heat/temperature to break down the $SrC{O_3}$ molecule.
Hence option C is the correct option. $SrC{O_3}$ is shown maximum thermal stability.

Note:
The melting point of Strontium carbonate ($SrC{O_3}$) is ${1497^O}C$.
Strontium carbonate ($SrC{O_3}$) is less soluble in ammonia and soluble in ammonium chloride.
The molecular mass of Strontium carbonate ($SrC{O_3}$) is $147.63g/mol$ and the colour of Strontium carbonate ($SrC{O_3}$) is white or grey in colour.