Question

Give reasons:
(i) Unlike alkali metal compounds, compounds of Li are much less soluble in water.
(ii) Although Li has highest I.E. in group –1 but it is the best reducing agent.
(iii) Li differs from other members of its group.
(iv) LiOH, $LiNO_{3}$, $Li_{2}CO_{3}$ decompose readily on heating, whereas the other alkali metal hydroxides & carbonates not decompose readily on heating.
(v) Alkali & some alkaline earth metals impart colour to bunsen flame.

Answer 1

i) The compounds of Lithium are covalent in nature and the other alkali metals are "ionic in nature". Hence the lithium compounds are less soluble in water

ii)  From its highest Ionization energy, we may assume that lithium is the weakest reducing agent of the alkali metals, but it has a strong standard electrode potential to act as a reducing agent

iii) Due to small size, the lithium atom has high ionization energy. Such that, it stays inactive to air without moisture, slowly reacts with water, liquid bromine and forms a highly stable hydride unlike other alkali metals.  

iv) Lithium nitrates, carbonates and hydroxides decomposes readily on heating because they are less stable to heat and forms oxides readily with the liberation of carbon dioxide

v) Alkali and some alkaline earth metals impart color to the Bunsen flame due to their low ionization enthalpies.