There is an increase in conductivity when Silicon is doped with Phosphorous. Give reason.

Explanation

### Step-by-Step Solution:

1. **Understanding Doping**: Doping is the process of adding impurities to a semiconductor to change its electrical properties. In this case, silicon (Si), which is a semiconductor, is being doped with phosphorus (P).

2. **Silicon's Structure**: Silicon has four valence electrons. In its crystalline structure, each silicon atom forms covalent bonds with four neighboring silicon atoms, utilizing all four of its valence electrons.

3. **Phosphorus Doping**: Phosphorus has five valence electrons. When phosphorus is introduced into the silicon lattice, it replaces some of the silicon atoms.

...