Question

Why phosphorus forms 3 bonds in molecule such as PH3 and PCl3-

Answer 1

Phosphorous has three lone electrons that need pairing. Similar to how carbon has 4 lone electrons, and forms CH4

Answer 2

The 3p orbital of the element will be completely filled if it forms 3 bonds with other atoms.

Step-by-step explanation:

Phosphorus is a element of 15 group and 3 period.

The electronic configuration of the phosphorous is:

1s²2s²2p⁶3s²3p³

The 3p orbital of phosphorous is singly filled by 3 electrons and if it shares more 3 electrons with other atom, its valence shell will be completely filled which makes it more stable. Hence, phosphorus makes 3 bonds like in PH₃ and PCl₃ .