Which of the following units is used to form cross-linked silicone?

Which of the following oxidation states are the most characteristic for lead and tin respectively?

The catenation tendency of $C, Si$ and $Ge$ is in the order $Ge < Si < C$. The bond energies (in $kJ \ mol^{-1}$) of $C-C, Si-Si$ and $Ge-Ge$ bonds,respectively,are:

What is meant by $Tin \ Cry$?

In the following reaction,identify the nature of the product formed by the complete hydrolysis of the underlined atom at $R.T.$:
$\underline{P}_4O_{10} + H_2O \longrightarrow H_3PO_4$

Which of the following species does not exist?