What are the common physical and chemical features of alkali metals?

(N/A) Physical properties of alkali metals:
$1$. They are quite soft and can be cut easily. Sodium metal can be easily cut using a knife.
$2$. They are light-coloured and are mostly silvery-white in appearance.
$3$. They have low density because of the large atomic sizes. The density increases down the group from $Li$ to $Cs$. The only exception to this is $K$,which has lower density than $Na$.
$4$. The metallic bonding present in alkali metals is quite weak. Therefore,they have low melting and boiling points.
$5$. Alkali metals and their salts impart a characteristic colour to flames. This is because the heat from the flame excites the electron present in the outermost orbital to a high energy level. When this excited electron reverts back to the ground state,it emits excess energy as radiation that falls in the visible region.
$6$. They also display the photoelectric effect. When metals such as $Cs$ and $K$ are irradiated with light,they lose electrons.
Chemical properties of alkali metals:
Alkali metals are highly reactive due to their low ionization enthalpy. As we move down the group,the reactivity increases.
$1$. They react with water to form their respective hydroxides and dihydrogen gas. The general reaction is: $2M + 2H_2O \longrightarrow 2M^{+} + 2OH^{\ominus} + H_2$.
$2$. They react with dihydrogen to form metal hydrides. These hydrides are ionic solids and have high melting points: $2M + H_2 \longrightarrow 2M^{+}H^{-}$.
$3$. Almost all alkali metals,except $Li$,react directly with halogens to form ionic halides: $2M + Cl_2 \longrightarrow 2MCl$ $(M = Li, K, Rb, Cs)$. Lithium halides are covalent in nature due to the high polarizing power of the small $Li^{+}$ ion.
$4$. They are strong reducing agents. The reducing power generally increases down the group,with $Li$ being the strongest reducing agent due to its high hydration energy.
$5$. They dissolve in liquid ammonia to form deep blue-coloured solutions,which are conducting and paramagnetic: $M + (x + y)NH_3 \to [M(NH_3)_x]^+ + [e(NH_3)_y]^-$. The blue colour is due to ammoniated electrons.