Incomplete octet

[JulieAljamal1E]

Are there any other elements or examples like Boron Trifluoride where the central atom can have an incomplete octet like boron does? Besides the first four elements of the periodic table (which never have a complete octet)

[Chris Freking 2G]

Aluminum can also sometimes have an incomplete octet for molecules like AlCl₃. However, AlCl₃ only exists at high temperatures--in normal temperatures, two molecules of AlCl₃ combine to form Al₂Cl₆ where both Al atoms obey the octet rule.

[905109118]

The common examples of such elements are hydrogen (stable with only 2 valence electrons), beryllium (stable with only 4 valence electrons) and boron and aluminum (stable with only 6 valence electrons).