Fill in the blanks:
$(1)$ Cement is also known as......
$(2)$ Cement was first introduced by......

Give a brief explanation of the ionisation enthalpy of alkaline earth metals (Group-$2$) elements.

Which alkaline earth metal sulfate has a hydration enthalpy value greater than its lattice enthalpy value?

Which property of alkaline earth metals increases with an increase in atomic number?

Which of the following statements is incorrect with reference to alkaline earth metals?

$A$ compound $X$ on heating gives a colourless gas. The residue is dissolved in water to obtain $Y$. Excess $CO_2$ is bubbled through the aqueous solution of $Y$ and $Z$ is formed. $Z$ on gentle heating gives back $X$. The compound $X$ is: