Is PH3 Polar or Nonpolar?

Answer: PH3 is polar due to the presence of a lone pair of electrons with electron-electron repulsion causing an overall "bent" structure. This results in a dipole moment throughout the molecule. 

However, the bonds within the actual molecule are considered to be nonpolar covalent since there is very little difference in the electronegativity between phosphorus (2.19) and hydrogen (2.20). Another reason why the lone pair creates a region of negative charge is because it does not have a corresponding proton to balance out the negative charge as the other bonds do. This essential +1 positive charge "balancer" encompasses the function of hydrogen within the other bonds.

PH3 has a similar structure to NH3 (ammonia) which makes sense since phosphorus and nitrogen are in the same group (pnictogens). You can read more about the Lewis Structure or Polarity of NH3 by clicking on the linked articles.

PH3 Ball and Stick Model
PH3 Ball and Stick Model. Created with MolView.
What state is PH3 normally found in?

PH3 is normally a colorless gas at standard temperature and pressure. The weak dipole interactions result in a boiling point of -87˚C which thereby makes this compound suitable as a "cryogenic liquid" (similar to the use of liquid nitrogen however at relatively less extreme temperatures). PH3 is said to have a very distinctive odor and can be flammable because of spontaneous formation of P2H4 within regions of PH3 buildup which can occur in certain places since PH3 is heavier than the atmosphere. Applications for PH3 include in certain Organic Chemistry reactions and as a pesticide for farm fields (agriculture).

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