Number of amphoteric compounds among the following is ...........
$A$. $BeO$
$B$. $BaO$
$C$. $Be(OH)_2$
$D$. $Sr(OH)_2$

Assertion $A$: Alkali metal elements impart characteristic colors to the flame in a flame test.
Reason $R$: They have very low ionization enthalpy.

State the reasons for the following:
$(a)$ Why is a solution of $Na_{2}CO_{3}$ alkaline?
$(b)$ Why are alkali metals prepared by the electrolysis of their fused chlorides?
$(c)$ Why is sodium found to be more useful than potassium in biological systems?

The correct order of increasing thermal stability of $K_2CO_3$,$MgCO_3$,$CaCO_3$ and $BeCO_3$ is

Which of the following alkali metal ions has the highest ionic mobility in aqueous solution?

The stability order of oxide,peroxide,and superoxide of alkali metals is: