why lithium hydrogen carbonate does not exist in solid form but others alkali metals do?
LiHCO3 is found in solution form while rest alkali metals hydrogen carbonates are solid due to the anomalous properties of Li and it's diagonal relationship with the Mg.
Following are the points of difference between Li and other alkali metals.
(i) it's exceptionally small size.
(ii)it's high polarizing power(charge/radius ratio).