VSEPR Practice Molecules and Ions
Here are forty-six molecules and ions that exhibit almost all the possibilities of molecular
geometry. They are listed in order of numbers of electron domains - "regions of high electron
density" - around the central atom(s). There are several molecules of each basic geometry. For
the purposes of VSEPR a multiple bond is counted as a single "domain", a single bond is a
"domain", and a lone pair (LP) is a "domain". In some molecules the preferred central atom is
underlined if there might be an ambiguity in writing the Lewis structure. In this list only one
molecule, C2H2, has two central atoms.
The five basic geometries of the electron domains (linear, trigonal planar, tetrahedral, trigonal
bipyramidal, and octahedral) are shown in Table 9.1, p. 319, Brown&LeMay. The thirteen
possible molecular geometries are shown in Tables 9.2, p. 321, and 9.3, p. 324.
2 domains - domain geometry is linear, 180° bond angle (sp hybridization)


molecular geometry is linear
Examples are:
CO2, HCN, BeCl2, C2H2
3 domains - domain geometry is trigonal planar, 120° bond angles (sp2 hybridization)
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no LP on central atom so molecular geometry is trigonal planar
Examples are:
NO3-, SO3, BF3, CO32

one LP on central atom so molecular geometry is bent
Examples are:
SO2, O3, NO2-, PbCl2
4 domains - domain geometry tetrahedral, 109.5° bond angles (sp3 hybridization)

no LP on central atom so molecular geometry is tetrahedral

Examples are:
CH4, XeO4, CCl4, SiH4, ClO4-, NH4+
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one LP on central atom so molecular geometry is trigonal pyramidal (tripod)
Examples are:
NH3, PF3, H3O+, XeO3, ClO3

two LPs on central atom so molecular geometry is bent
Examples are:
H2O, OF2, H2S, SF2
5 domains - domain geometry trigonal bipyramidal, 90°/120° bond angles (sp3d hybridization)
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
no LP on central atom so molecular geometry is trigonal bipyramidal
Examples are:
PCl5, SOF4, AsF5
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one LP on central atom so molecular geometry is see-saw
Examples are:
SF4, IF4+, IO2F2-, XeO2F2
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two LPs on central atom so molecular geometry is T-shaped
Examples are:
ClF3, BrF3
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
three LPs on central atom so molecular geometry is linear
Examples are:
XeF2, I3-, IF2-
6 domains - domain geometry octahedral, 90° bond angles (sp3d2 hybridization)
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
no LP on central atom so molecular geometry is octahedral
Examples are:
SF6, IOF5
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one LP on central atom so molecular geometry is square pyramidal
Examples are:
IF5, TeF5-, XeOF4
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two LPs on central atom so molecular geometry is square planar
Examples are:
XeF4, ICl4-
Here are the same forty-six molecules and ions in random order. Write the Lewis structure and
determine the domain geometry for each. Then predict the molecular geometry and find it in the
above table to check.
NO3-, TeF5-, SF4, CO32-, H2S, PCl5, BF3, NH4+, AsF5, HCN, XeO2F2,
ClO4-, XeF4, I3-, H3O+, ClF3, SO2, O3, NO2-, XeOF4, PF3, SF6, CH4,
XeF2, XeO4, SO3, CCl4, SiH4, PbCl2, NH3, XeO3, ClO3-, H2O, OF2, SF2,
CO2, SOF4, IF4+, IO2F2-, BeCl2, BrF3, IF2-, IOF5, IF5, C2H2, ICl4-
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