跪救: ICl3 (20分)

The shape of molecule is included in the present HKAL syllabus.

First of all, you have to recognize that the central atom is I, which has 7 valence electrons and expands its octet in forming ICl3.

In forming ICl3, each of 3 valence electrons of I forms an I-Cl single bond, and the 4 electrons left as 2 lone pairs of electrons. There are totally 5 electron pairs in the central I atom.

According to Valence Shell Electron Pair Repulsion Theory (VSEPR Theory), the 5 electrons pairs are arranged as triangular bipyramidal in shape. Since the lone pairs exert greater repulsions to other electrons pairs than bond pairs, the 2 lone pairs thus locate on the triangular plane. Only bonding atoms are consider in determination of the shape of the molecule, and thus ICl3 is T-shaped.

The shape of ICl3 is shown below:


圖片參考：http://i320.photobucket.com/albums/nn347/old-master/090730_1.jpg?t=1248968939


http://i320.photobucket.com/albums/nn347/old-master/090730_1.jpg?t=1248968939

http://en.wikipedia.org/wiki/Iodine_trichloride