(i) Lithium metal is used to make useful alloys. For example with lead it is used to make 'white metal' bearings for motor engines, with aluminium to make aircraft parts, and with magnesium to make armour plates. It is used in thermonuclear reactions.
(ii) Lithium is also used to make electrochemical cells.
(iii) Lithium carbonate is used in medicines
(iv) Sodium is used to make Na/Pb alloy.
(v) Liquid sodium metal is used as a coolant in fast breeder nuclear reactors.
(vi) Potassium chloride is used as a fertilizer. Potassium hydroxide is used in the manufacture of soft soap. It is also used as an excellent absorbent of carbon dioxide.
(vii) Caesium is used in devising photoelectric cells.

(i) Alkali metals dissolve in liquid ammonia to give deep blue solutions that are conducting in nature
(ii) The blue colour of the solution is due to the ammoniated electron which absorbs energy in the visible region of light and thus imparts blue colour to the solution.
(iii) The solutions are paramagnetic and on standing slowly liberate 'hydrogen resulting in the formation of amide
(iv) In concentrated solution' the blue colour changes to bronze colour and become diamagnetic·

(i) All alkali metals react with hydrogen at about 673K (lithium at 1073K) to form the corresponding hydride which are ionic 10 nature.
(ii) Reactivity of alkali metals with hydrogen increases from Li to Cs
2M + H₂ ⟶ 2M⁺H^- (M= Li,Na,K,Rb,Cs)
(iii) Ionic character of the hydrides increases from Li to Cs.
(iv) The decrease in ionization enthalpy down the group permits easy availability of electrons to hydrogen, forming H⁺ ion.
(v) The hydrides behave as strong reducing agents and their reducing nature increases down the group.

i) The fact that a small cation can stabilize a small anion and a large cation can stabilize a large anion explains the formation and stability of these oxides.
(ii) The Na⁺ ion is a larger cation and has a weak positive field around it and thus can stabilize a bigger peroxide ion, O₂^2- or [-O-O-]²- which is also surrounded by a weak negative field.
(iii) Similarly, the other ions K⁺, Rb⁺, Cs⁺ are still larger, having very weak positive field·
(iv) Thus these ions can stabilize a bigger superoxide O^2- anion and form super oxides·