Question #931d5

1 Answer
Ernest Z.
Feb 25, 2017

The phosphorus atoms in elemental phosphorus, #P"_4#, are probably unhybridized.

Explanation:

We know that elemental phosphorus has a tetrahedral structure.

Hence, the Lewis structure is

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Each P atom has a lone pair and 3 bond pairs, for a steric number, #"SN = 4"#.

VSEPR theory predicts an #"sp"^3# hybridization, with normal bond angles of 109.5°.

Compression from 109.5° to 60° would involve enormous angle strain.

If phosphorus used its unhybridized #"3p"# orbitals, the compression would be only(?) from 90° to 60°, but this is still a huge amount of angle strain.

More likely, each #"3p"# orbital keeps its 90° bond angle for overlap with the orbitals of the other phosphorus atoms.

3p overlap
(Adapted from Chemexplore)

These bonds would not be as strong as ordinary σ bonds because the overlap angles are 90°.

Chemists usually call such bonds "bent bonds" or "banana bonds" because they are bent like a banana.

Banana bonds
(Adapted from Chemexplore)

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