Which of the following is the most important biological compound containing $Mg$ found in the living world?

The lustre of a metal is due to

Among the following metals,which one has the lowest probable interatomic forces?

The alkali metal halides are soluble in water but $LiF$ is insoluble because

The strongest reducing agent among the alkali metals is

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 ......