All the alkali metals have an electron in their outermost shell and all the alkaline earth metals have two outer electrons. To achieve the noble gas configuration, alkali metals need to lose one electron (valence is “one”), whereas alkaline earth metals need to remove two electrons (valence is “two”).

All of the above because alkali metal carbonates are more stable and also the trend of solubility is opposite in both of them.In former it increases down the grp while in latter it dec down the grp

Stability of Carbonates:
- The stability of carbonates refers to how easily they decompose or break down.
- Carbonates of alkali metals such as sodium carbonate (Na2CO3) and potassium carbonate (K2CO3) are highly stable and do not decompose easily.
- On the other hand, carbonates of alkaline earth metals such as calcium carbonate (CaCO3) and magnesium carbonate (MgCO3) are less stable and decompose relatively easily at high temperatures.

Lattice Enthalpy of Carbonates:
- Lattice enthalpy refers to the energy required to separate one mole of an ionic solid into its constituent ions in the gas phase.
- The lattice enthalpy of carbonates generally decreases as we move down the alkali metal and alkaline earth metal groups.
- This is because the size of the cation increases down the group, leading to a decrease in the electrostatic forces of attraction between the cations and anions in the lattice.
- As a result, the lattice enthalpy decreases, indicating that the carbonates become less stable and easier to decompose.

Solubility of Carbonates:
- Solubility refers to the ability of a substance to dissolve in a solvent.
- Carbonates of alkali metals are highly soluble in water. For example, sodium carbonate and potassium carbonate readily dissolve in water to form alkaline solutions.
- On the other hand, carbonates of alkaline earth metals are less soluble in water. For example, calcium carbonate and magnesium carbonate have lower solubilities and tend to form precipitates in water.

Explanation of Answer:
- The given answer, option D, states that the carbonates of alkali and alkaline earth metals differ in terms of stability, lattice enthalpy, and solubility.
- This is supported by the differences discussed above.
- Alkali metal carbonates are more stable, have higher lattice enthalpies, and are more soluble in water compared to alkaline earth metal carbonates.
- Therefore, option D is the correct answer as it encompasses all the differences between the carbonates of alkali and alkaline earth metals.