its lighter congener BF3. In contrast, the extra stability of the 7p1/2 electrons in tennessine are predicted to make TsF3 trigonal planar, unlike the T-shaped geometry observed for IF3 and predicted for AtF3; similarly, OgF4 should have a tetrahedral geometry, while XeF4 has a square planar geometry and RnF4 is predicted to have the same. Odd-electron molecules The VSEPR theory can be extended to molecules with an odd number of electrons by treating the unpaired electron as a "half electron pair" — for example, Gillespie and Nyholm suggested that the decrease in the bond angle in the series (180°), NO2 (134°), (115°) indicates that a given set of bonding electron pairs exert a weaker repulsion on a single non-bonding electron than on a pair of non-bonding electrons. In effect, they considered nitrogen dioxide as an AX2E0.5 molecule, with a geometry intermediate between and . Similarly, chlorine dioxide (ClO2) is an AX2E1.5 molecule, with a geometry intermediate between and . Finally, the methyl radical (CH3) is predicted to be trigonal pyramidal like the methyl anion (), but with a larger bond angle (as in the trigonal planar methyl cation ()). However, in this case, the VSEPR prediction is not quite true, as CH3 is actually planar, although its distortion to a pyramidal geometry requires very little energy. See also Valence Bond Theory (VBT) Molecular Orbital Theory (MOT) Bent's rule (effect of ligand electronegativity) Linear combination of atomic orbitals Molecular geometry Molecular modelling Comparison of software for molecular mechanics modeling Thomson problem Valency interaction formula References Further reading External links VSEPR AR - 3D VSEPR Theory Visualization with Augmented Reality app 3D Chem – Chemistry, structures, and 3D Molecules IUMSC – Indiana University Molecular Structure Center Chemistry theories Molecular geometry Stereochemistry Quantum chemistry