Answer:

The formation of solid hydrogen carbonate:
Solid hydrogen carbonate compounds are formed when a metal reacts with carbonic acid (H2CO3). The reaction results in the formation of metal hydrogen carbonate salts, also known as bicarbonates. These salts have the general formula M(HCO3)n, where M represents the metal cation and n represents the valency of the metal.

Elements that form solid hydrogen carbonate:
1. Sodium (Na): Sodium forms solid hydrogen carbonate (sodium bicarbonate) with carbonic acid. The chemical equation for the reaction is:
Na2CO3 + H2O + CO2 → 2NaHCO3

2. Potassium (K): Potassium also forms solid hydrogen carbonate (potassium bicarbonate) with carbonic acid. The chemical equation for the reaction is:
K2CO3 + H2O + CO2 → 2KHCO3

3. Caesium (Cs): Caesium can also form solid hydrogen carbonate (caesium bicarbonate) with carbonic acid. The chemical equation for the reaction is:
Cs2CO3 + H2O + CO2 → 2CsHCO3

Element that does not form solid hydrogen carbonate:
4. Lithium (Li): Lithium does not form solid hydrogen carbonate (lithium bicarbonate) with carbonic acid. Instead, it forms lithium carbonate (Li2CO3) and water. The chemical equation for the reaction is:
Li2CO3 + H2O → Li2O + CO2 + H2O

Explanation:
The reason why lithium does not form solid hydrogen carbonate is due to the lower stability of lithium bicarbonate compared to lithium carbonate. Lithium bicarbonate is highly unstable and decomposes into lithium carbonate and water. Therefore, lithium carbonate is the more thermodynamically favorable product in the presence of carbonic acid.

On the other hand, sodium, potassium, and caesium bicarbonates are stable and do not readily decompose. These metals have larger ionic radii and lower electronegativities compared to lithium, which allows them to stabilize the bicarbonate ion (HCO3-) more effectively. As a result, sodium, potassium, and caesium can form solid hydrogen carbonates.

In summary, while sodium, potassium, and caesium can all form solid hydrogen carbonates, lithium does not have this ability due to the instability of lithium bicarbonate.