Silicon dissolves in excess of $HF$ due to the formation of:

Identify $(P)$ and $(Q)$ in the following reaction:
$2 CH_3 Cl + Si$ $\xrightarrow[570 \ K]{\text{Cu powder}} (P)$ $\xrightarrow{H_2 O} (Q)$ $\longrightarrow \text{Straight chain polymer}$

When silicate units are linked together,they form which type of structures?

In the following reaction,assign the nature of the product formed by the complete hydrolysis of the underlined atom at $R.T.$: $\underline{C}O + H_2O \longrightarrow \text{No reaction}$

Which of the following elements has the lowest melting point?

The group $14$ elements $A$ and $B$ have the first ionisation enthalpy values of $708$ and $715 \ kJ \ mol^{-1}$ respectively. These values are the lowest among their group members. The nature of their ions $A^{2+}$ and $B^{4+}$ respectively is: