$Na_2CO_3$ is manufactured by the Solvay process. The products that are recycled are:

Lithium shows diagonal relationship with

Which of the following is the superoxide of potassium?

$A$ metal $(A)$ on heating in nitrogen gas gives compound $(B)$. $(B)$ on treatment with $H_{2}O$ gives a colourless gas which when passed through $CuSO_{4}$ solution gives a dark blue-violet coloured solution. $(A)$ and $(B)$ respectively,are

$Cs^{+}$ ions impart violet colour to Bunsen flame. This is due to the fact that the emitted radiations are of

With the increase in atomic weights,the melting points of the alkali metals: