Which of the following substances is insoluble in water?

Assertion : Both $Be$ and $Al$ can form complexes such as $BeF_4^{2-}$ and $AlF_6^{3-}$ respectively,$BeF_6^{3-}$ is not formed.
Reason : In case of $Be$,no vacant $d-$ orbitals are present in its outermost shell.

The major ingredient $(51 \%)$ in Portland cement is

Discuss the trend of the following:
$(i)$ Thermal stability of carbonates of Group $-2$ elements.
$(ii)$ The solubility and the nature of oxides of Group $-2$ elements.

Why does the solubility of alkaline earth metal carbonates and sulphates decrease down the group?

Which of the following alkaline earth metal hydroxides is the least soluble in water?