The number of electrons in the valence shell of calcium is

An alkaline earth metal $M$ readily forms water-soluble sulphate and water-insoluble hydroxide. Its oxide $MO$ is very stable to heat and does not have rock-salt structure. $M$ is :-

When a metal is burnt in air,the resulting ash,upon moistening,gives the smell of $NH_3$. Which metal is it?

The correct order of density in the $IIA$ group (alkaline earth metals) is:

In India,green flames are observed during fireworks at weddings. Which of the following elements is responsible for this?

$Ra$ (Radium) is placed at the bottom of the alkaline earth metals. Which of the following is true for this element?