When phosphorus is added to silicon, it forms bonds with four silicon atoms, contributing an extra electron to the lattice structure. The reason phosphorus does not bond with a fifth silicon atom is due to the spatial constraints of the silicon lattice, which is tetrahedral in nature. There is no physical space for a fifth silicon atom, and the bonding geometry does not allow for such an arrangement. The discussion also clarifies that the covalent bonds among silicon atoms in the lattice are not considered intermolecular bonds, as intermolecular bonds refer to interactions between distinct molecules, and the silicon lattice does not consist of separate molecules.
