Are the bonds in phosphine examples of nonpolar or polar covalent bonds?

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t-nez | High School Teacher | (Level 3) Associate Educator

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Phosphine is an example of a polar molecule with non-polar bonds. It has the formula PH3. The phosphorus is bonded to three hydrogen atoms and has a lone pair of electrons. Since hydrogen and phosphorus are equal in electronegativity, meaning that they attract the shared pairs of electrons the same amount, the bonding electrons are shared equally making the covalent bonds non-polar. 

The lone pair of electrons on phosphorus causes the molecule to be asymmetrical with respect to charge distribution and that's why the molecule is polar even though it has non-polar bonds. Its shape is trigonal pyramidal.

Phosphine is a highly poisonous gas and is pyrophoric, meaning that it burns spontaneously in air. It's used as a fumigant to kill insects and rodents in stored grain and feed. It's applied as a phosphide compound that releases phosphine when it reacts with water, in a concentration not likely to ignite.

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