Question

What atomic or hybrid orbitals make up the sigma bond between Al and Cl in aluminum chloride, AlCl3 ?

_____orbital on Al +_____ orbital on Cl

What is the approximate Cl-Al-Cl bond angle ? ____ °

Answer 1

Count the number of valence electrons around the Al atom in AlCl₃. Note that AlCl₃ is partly covalent and partly ionic.

Al: 3

Cl: 3

Total number of valence electrons = (3 + 3) = 6

6 valence electrons around the central atom can be arranged in a trigonal planer arrangement. Therefore, the central Al atom in AlCl₃ has trigonal planer electronic geometry. A trigonal planer geometry results from sp² hybridization of the central atom; consequently, the Al atom in AlCl₃ has sp² geometry.

The valence electrons in Cl reside in the 3p orbitals. Since the valence electrons are involved in bonding only, hence, the bonding in AlCl₃ is between sp²(Al)-3p(Cl) orbitals.

The Cl-Al-Cl bond angle in AlCl₃ is 120º (ans).