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Exceptions to the Octet Rule

Elements that go below the octet rule:

Boron and Beryllium-These 2 elements tend to violate the octet rule by having fewer than 8 electrons around them.

Example Lewis Dot Videos- 

Lewis Dot of Beryllium Fluoride   BeF2

Lewis Dot of Boron Trichloride   BCl3    (also BF3)

Lewis Dot of Borane   BH


Elements that exceed the octet rule:

This behavior is observed for elements in Period 3 and beyond.  This occurs because elements in period 3 have access to the 3d sublevel in addition to the 3s and 3p. Elements in period 2 only have access to 2s and 2p. So these elements can only hold 8 valence electrons, while elements in period 3 and beyond "have access to another sublevel" and may sometimes exceed the octet rule.

Example Lewis Dot Videos- 

Lewis Dot of Sulfur Hexafluoride   SF6

Lewis Dot of Phosphorous Pentachloride  PCl5

Lewis Dot of Xenon Oxytetrafluoride  XeOF4


Structures that could but Don't break the octet rule:

Lewis Dot of Sulfur Dioxide  SO2

Lewis Dot of Sulfur Trioxide  SO3

Chemical Demonstration Videos