Consider the following molecular shapes:
(a) Match each shape with one of the following species: XeF3+, SbBr3, GaCl3.
(b) Which, if any, is polar?
(c) Which has the most valence electrons around the central atom?
Step 1: (a)
Here, we are going to match the shape of the species.
For determining the shape, we have to use VSEPR theory.
The valence-shell electron-pair repulsion (VSEPR) theory is based on the electron groups around the central atom.
An electron group can be an electron pair, a lone pair, a single unpaired electron, a double bond or a triple bond on the center atom. VSEPR theory can help to predict the shape of a molecule.
According to VSEPR theory,
- The geometry of a molecule is determined by the number of electron groups on the central atom.
- The number of electron groups is determined from the Lewis structure of the molecule.
- The geometry of the electron groups is determined by their repulsions
Lone pair–lone pair > lone pair–bonding pair > bonding pair–bonding pair
Lewis structure of XeF3+:
Valence electrons of Xe is 8 (Group VIIIA)
Valence electrons of F is 7 (Group VIIA)
Total valence electrons of XeF3+ is (37 +8 -1 =28)
Here, each Xe atom is surrounded by five electron groups around it. Therefore, its electron-group arrangement is trigonal bipyramidal. Thus, the molecular shape of XeF3+ is T-shape due to presence of lone pair of electrons
Therefore, the ideal angle for F-Xe-F is <90o.
Thus, XeF3+ matches with the diagram A.