Phosphorus has an electronic configuration in the simple form 2,8,5 and a spdf configuration of 1s² 2s² 2p⁶ 3s² 3p³.
The valence electrons in phosphorus (the electrons available for bonding) are 5. As a result, an atom of phosphorus shares its electrons with another atom to form COVALENT bonds. This is ideal since it would take a high amount of energy to release these five electrons, and it would be unlikely for atoms to lose 5 electrons to donate to phosphorus.