Answer:
The concept that compounds containing carbon, nitrogen, oxygen, and fluorine are more stable if these atoms have eight valence electrons. When one of these atoms has less than eight valence electrons it has an open octet. The terms 'full octet' and 'full valence electron count' are not interchangeable (although they are often used this way), as eight is not the preferred valence electron count for all elements. Likewise the terms 'open octet' and 'open valence electron count' are also not interchangeable
