Which of the following metals will give $H_2$ gas on reaction with $NaOH$?

Fill in the blanks:
$(1)$ Among all alkali metals,.......... is a radioactive element.
$(2)$ The half-life of $^{223}Fr$ is ..........
$(3)$ Among all alkali metal ions,............ has the highest ionization enthalpy.
$(4)$ Alkali metals are identified by the ........... test.

Identify $X$ and $Y$, respectively in the following reactions:

Lithium shows diagonal relationship with element $X$ and aluminum with $Y$. $X$ and $Y$ respectively are

Which of the following is the correct order of increasing solubility for the given compounds?

What are the by-products in the Solvay process for the production of $Na_2CO_3$?