Two alkali halide salts,$ACl$ and $BCl$,gave crimson red and violet colors in their flame tests,respectively. $A$ and $B$ are respectively:

Which among the following elements is used in devising photoelectric cells?

When substance $A$ reacts with water,it produces a combustible gas $B$ and a solution of substance $C$ in water. When another substance $D$ reacts with solution $C$,it produces the same gas $B$,even when reacting with dilute sulfuric acid at room temperature. $A$ gives a golden yellow flame in a Bunsen burner flame. What are $A, B, C,$ and $D$ respectively?

Which of the alkali metals has the lowest melting point?

What is the correct stability order of $KO_2$, $RbO_2$, and $CsO_2$?

The weakest base among $KOH$,$NaOH$,$Ca(OH)_2$,and $Zn(OH)_2$ is: