Bone black is a form of which element?

Assertion $(A): [SiF_6]^{2-}$ is formed but $[SiCl_6]^{2-}$ is not.
Reason $(R):$ Electronegativity $(EN)$ of $F$ is higher than $EN$ of $Cl$.

Given below are the atomic numbers of some group $14$ elements. The atomic number of the element with the lowest melting point is:

The main reason that $SiCl_{4}$ is easily hydrolysed as compared to $CCl_{4}$ is that

Which one of the following oxides is expected to exhibit paramagnetic behaviour?

Which of the following statements is correct for the compounds $HF, HBr, H_2Se, H_2Te, H_3P$?