Lewis Structure of PH₃ (Phosphine)
What is the Lewis structure of PH₃?
PH₃ has 8 valence electrons, 3 bonding electron pairs, and 1 lone pair. Phosphine has 8 valence electrons. Six are in three P-H bonds and 2 form a lone pair on phosphorus. The lone pair gives PH₃ its trigonal pyramidal shape, similar to ammonia.
| Formula | PH₃ |
| Name | Phosphine |
| Total Valence Electrons | 8 |
| Lone Pairs | 1 |
| Has Resonance | No |
| Concept | Lone Pairs |
| Difficulty | Beginner |
Step 1: Count Valence Electrons
P (Group 5A) has 5 valence electrons, each H has 1: 5 + 3(1) = 8 total.
Step 2: Draw the Skeleton
Phosphorus is central, bonded to 3 hydrogens. Three bonds use 6 electrons.
Step 3: Distribute Lone Pairs
2 electrons remain and form 1 lone pair on phosphorus, completing its octet.
Step 5: Check Formal Charges
- P: FC = 5 - 2 - ½(6) = 0
- H: FC = 1 - 0 - ½(2) = 0
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