$Na_2CO_3 \xrightarrow{\Delta} A$,'$A$' is

In view of their low ionisation energies,the alkali metals are:

The alkali metals dissolve in liquid $NH_3$. Which of the following statements is correct?

For the alkali metals,which of the following increases with increasing atomic number?

Fill in the blanks:
$(1)$ ......... method is used to prepare sodium carbonate.
$(2)$ Sodium carbonate exists as .........
$(3)$ Sodium chloride is commonly known as .........
$(4)$ Sodium chloride melts at ......... temperature.

Carnallite is a mineral of