Exceptions to the Octet Rule
Reminder about the Octet Rule
"Atoms tend to gain, loseor shareelectrons until they are surrounded by 8 valence electrons"
Exceptions to the Octet Rule
- Atoms with a total odd number of electrons
- Less than Octet
- More than Octet
Example on Atoms with a total odd number of electrons: NO Molecule
Total number of valence electrons = 5 (of N) + 6 (of O) = 11 (odd number)
Example on Less than Octet: BF3 Molecule
Despite these correct resonance structures, they are not possible due to the unacceptable formal charge on F.
Example on More than Octet: PCl5 Molecule
- Where the central atom (P) is surrounded by more than octet (8).
- This is observed in elements where the 3rd shell(and beyond) are being filled
- Here, the outermost configuration of P is: 3s2, 3p3, 3d0
- Such elements exceed octet by accommodating more electrons in their empty d orbitals
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Date of last modification: 2021