Explain the following :

Boron does not exist as ${\mathrm{B}}^{3+}$ ion.

Explain the following :

Aluminium forms $[{\mathrm{AlF}}_6{]}^{3–}$ ion but boron does not form $[{\mathrm{BF}}_6{]}^{3–}$ ion.

Explain the following :

${\mathrm{PbX}}_2$ is more stable than ${\mathrm{PbX}}_4$.

Explain the following :

Electron gain enthalpy of chlorine is more negative as compared to fluorine.

Explain the following :

$\mathrm{Tl}({\mathrm{NO}}_3{)}_3$ acts as an oxidising agent.

Explain the following :

Carbon shows catenation property but lead does not.

Explain the following :

${\mathrm{BF}}_3$ does not hydrolyse.

Explain the following :

Why does the element silicon, not form a graphite like structure whereas carbon does.