Which element from the following is used for cancer treatment?

How is calcium sulphate obtained?

The compound $A$ on heating gives a colourless gas and a residue that is dissolved in water to obtain $B$. Excess of $CO_2$ is bubbled through aqueous solution of $B$,$C$ is formed which is recovered in the solid form. Solid $C$ on gentle heating gives back $A$. The compound $A$ is:

Choose the correct statement$(s)$:
$A.$ Beryllium oxide is purely acidic in nature.
$B.$ Beryllium carbonate is kept in the atmosphere of $CO_2$.
$C.$ Beryllium sulphate is readily soluble in water.
$D.$ Beryllium shows anomalous behavior.
Choose the correct answer from the options given below:

Which element among the alkaline earth metals primarily forms covalent compounds?

The oxide,which is best soluble in $H_2O$ is