Which of the following is an alkali metal?

Identify the product when magnesium burns in air.

Assertion : $K$,$Rb$ and $Cs$ (all belonging to group $1$) can also form superoxides.
Reason : The ionic radii of $K$,$Rb$ and $Cs$ show the following trend $Cs^{+} < Rb^{+} < K^{+}$.

Which of the following properties is $NOT$ correct for alkali metals?

Which of the following is most basic in character?

$A$ certain metal $M$ is used to prepare an antacid,which is used as a medicine for acidity. This metal accidentally catches fire,which cannot be extinguished by using $CO_2$ based extinguishers. The metal $M$ is