Valency of silicon with respect to hydrogen is

4

Let us analyze the electronic configuration of silicon and its behavior in bonding:

1. Electronic Configuration of Silicon:
   The atomic number of silicon is 14. Its electronic configuration is:
   1s² 2s² 2p⁶ 3s² 3p²
   From this configuration, we can observe that the outermost shell (third shell) of silicon contains 4 electrons (2 in the 3s subshell and 2 in the 3p subshell). These are called valence electrons.
2. Valency Concept:
   Valency is the ability of an atom to form bonds by losing, gaining, or sharing electrons to complete its octet (8 electrons in the outermost shell). Silicon has 4 electrons in its outer shell and needs 4 more electrons to complete its octet. Therefore, silicon shares its 4 valence electrons with other atoms to form covalent bonds.

3. Silicon's Bonding with Hydrogen:
   When silicon reacts with hydrogen, it forms silane (SiH₄). In this molecule:

   • Silicon shares each of its 4 valence electrons with 4 hydrogen atoms.
   • Each hydrogen atom contributes one electron, allowing silicon to complete its octet.

   The structure of silane (SiH₄) demonstrates that silicon forms 4 covalent bonds with hydrogen, indicating a valency of 4.

4. Significance in Chemistry:
   • This tetra-valency makes silicon versatile in forming compounds, especially in the field of organic chemistry and materials science.
   • Silicon's ability to bond with hydrogen is foundational for silicon-based compounds, including silanes and silicones.

The valency of silicon with respect to hydrogen is four, as it forms four covalent bonds with hydrogen atoms in compounds like SiH₄. This arises from its electronic configuration and the need to complete its octet.