Which one of the following elemental forms is not present in the enamel of the teeth?

Which of the following statements are correct ? Choose the most appropriate answer from the options given below:

The correct order of melting point is :

Which one of the following alkaline earth metal ions has the highest ionic mobility in its aqueous solution?

The number of alkali metal(s), from Li, K, Cs, Rb having ionization enthalpy greater than 400 kJ $\mathrm{mol}^{-1}$ and forming stable super oxide is___.

$\mathrm{Mg}\left(\mathrm{NO}_3\right)_2 \cdot \mathrm{XH}_2 \mathrm{O}$ and $\mathrm{Ba}\left(\mathrm{NO}_3\right)_2 \cdot \mathrm{YH}_2 \mathrm{O}$, represent formula of the crystalline forms of nitrate salts. Sum of $X$ and $Y$ is $\_\_\_\_$

For a good quality cement, the ratio of lime to the total of the oxides of Si, Al and Fe should be as close as...

Alkali metal from the following with least melting point is:

Given below are two statements: One is labelled as Assertion A and the other is labelled as Reason R
Assertion A: Sodium is about 30...