The most soluble bicarbonate is

When sodium is dissolved in liquid $NH_3$,the solution becomes blue due to the presence of:

Which of the following compounds is used as a fire extinguisher?

Fill in the blanks:
$(1)$ Lithium on reaction with nitrogen present in air is denoted by .....
$(2)$ Potassium gives ...... colour in oxidizing flame.
$(3)$ ....... and ........ metals are used in photoelectric cells.
$(4)$ When alkali metal dissolves in ammonia,it produces a blue-coloured solution. This colour is due to .......

Assertion $(A)$: Alkali metals are soft and have low melting and boiling points.
Reason $(R)$: This is because interatomic bonds are weak.

Calcium is obtained by