Answer:

Lithium hydroxide (LiOH) is considered the least basic hydroxide among the alkali metals because of its smaller ionic size and higher charge density compared to other alkali metal ions.

As we move down the alkali metal group (Li, Na, K, Rb, Cs), the ionic size increases due to the addition of electron shells. Larger ionic size results in weaker electrostatic interactions between the metal cation and the hydroxide ion (OH^-). This weaker interaction makes it easier for the hydroxide ion to dissociate and release hydroxide ions in solution, leading to a stronger basicity.

Lithium (Li) is the smallest alkali metal, and its small size causes stronger electrostatic interactions with the hydroxide ion, making it more difficult for the hydroxide ion to dissociate. As a result, lithium hydroxide exhibits lower basicity compared to the hydroxides of other alkali metals.