Why is there an empty #p# orbital in #"Al"# of #"AlCl"_3?#

1 Answer
Nov 26, 2017

Per the literature, #AlCl_3# is defined as a trigonal planer geometry based on three #sp^2# hybrid orbitals from the aluminum. The 3rd p-orbital is simply not involved in the hybridization.

Explanation:

#Al [Ne]3s^(2)3p_x^1p_y^0p_z^0# => #Al[Ne]3(sp^2)^(1)1(p_z^0)# => Trigonal Planar geometry.

The extra p-orbital is simply not included in the hybridization needed to attach 3 substrates to the central element, Al. Only an s and 2 p-orbitals are needed.

http://www.tutor-homework.com/Chemistry_Help/Molecular_Geometry/009_Aluminum_Trichloride_AlCl3.html