Question

Among the carbonates of alkali metals which one has highest stability:
A.$\;C{s_2}C{O_3}$
B.$R{b_2}C{O_3}$
C.${K_2}C{O_3}$
D.$N{a_2}C{O_3}$

Answer 1

In order to solve this question, we need to understand the characteristics of the compounds of alkali metals. The chemical elements lithium, sodium, potassium, rubidium, caesium, and francium make up the alkali metals. Together with hydrogen, they form group 1, which is located in the periodic table's s-block.

Complete step by step answer:
Stability is described as the capacity of the bound molecules to withstand the impact of heat while retaining their characteristics. In other words, the maximum temperature at which a molecule may be heated without losing its characteristics. The alkali metals are more similar to one another than any other group of elements are. Moving down the table, for example, all known alkali metals exhibit rising atomic radius, decreasing electronegativity, increasing reactivity, and lowering melting and boiling temperatures, as well as heats of fusion and vaporization.
The Cause of the Increasing and Decreasing The thermal stabilities are listed below. Sizes – Thermal stability is generally proportional to the size of the element and rises as one moves down the group. The thermal stability rises as we proceed from lithium to cesium due to the increase in size. The larger the complex, the more heat is required to break down it.
Charge density - The charge density is inversely proportional to the positive ion's size. As a result, the influence on carbonate ions rises. As the positive ion moves along the group, the charge density drops, reducing the influence on the carbonate ion and therefore enhancing the thermal stability of the compound.
Structure - The structure of the material has a significant impact on its thermal stability, and the structure is dependent on the bonds between atoms that keep the structure together. Charges are delocalized — carbonate contains two single carbon-oxygen bonds and one double bond in its structure. The two oxygen atoms are both negatively charged. The charges of carbonate ion are spread throughout the ion, with a higher concentration on oxygen atoms. Charges can also be said to be delocalized.
Metal carbonates become more stable as we move down the group. The bigger molecules further down require more heat to break down than the lighter ones. So $\;C{s_2}C{O_3}$has the best thermal stability of the carbonates tested.

Hence, the correct option is option A.

Note:
It must be noted that the alkali metals easily react with carbon dioxide to form carbonates and bicarbonates. All alkali metals contain an s-orbital outermost electron; this common electron configuration leads to extremely similar characteristic characteristics. Indeed, the alkali metals are the finest illustration of periodic table group trends in characteristics, with elements displaying well-characterized homologous behaviour. This element family is also known as the lithium family for its leader element, lithium.