The nitrate of which metal does not give nitrogen dioxide on strong heating?

Which of the following metals is not found in the free state?

Fill in the blanks:
$(1)$ $Li-Mg$ alloy is used to prepare ......
$(2)$ Colors of superoxides of alkali metals are ...... or ......
$(3)$ On combustion of lithium in the presence of air,it produces ...... and ......
$(4)$ On heating,lithium nitrate converts into ......

The metal-pair that can produce nascent hydrogen in alkaline medium is

Beryllium is placed above magnesium in Group $2$. What happens when beryllium powder is added to a solution of $MgCl_2$?

The alkali metals form salt-like hydrides by direct synthesis at elevated temperatures. The thermal stability of these hydrides decreases in which of the following orders?