1. Bonding Theories Summary Edward A. Mottel Department of Chemistry Rose-Hulman Institute of Technology

2. 6/10/2015 Bonding Theories  Ionic Model  Skeleton Diagrams  Lewis Dot Diagrams  Molecular Orbital Theory  Orbital Hybridization  Valence Bond Theory  Valence Shell Electron Pair Repulsion

3. 6/10/2015 Ionic Model  The coulombic attraction of charged particles in a 3-D lattice describes bonding.  Compounds usually have high melting points unless decomposition occurs.  Applicable to single ions, radicals, complex ions, polyatomic ions, etc.  Examples NaCl, CaF 2, BaSO 4, PbCrO 4, etc.

4. 6/10/2015 Skeleton Diagrams  The tendency of first and second row elements (n = 1, 2) to form covalent molecules with a specific number of bonds can be used to derive reasonable bonding arrangements.

5. 6/10/2015 Skeleton Diagrams  Most physical and structural properties are not predicted by this theory. (e.g., magnetic properties, shape, polarity, color)  Examples CO 2, NH 3, BF 3, Be(OH) 2, etc.

6. 6/10/2015 Lewis Dot Diagrams  Electron pair concept allows the prediction for the possible arrangement of nuclei by adhering to the duet and octet (inert gas configuration) rule.  Calculation of formal charges can further identify the most stable arrangement.

7. 6/10/2015 Lewis Dot Diagrams  Valid for most compounds composed of first and second row elements.  Examples CO, CO 2, H 2 O, CH 4, NH 4 +, N 2, etc.

8. 6/10/2015 Molecular Orbital Theory  Theory describes the arrangement of electrons between two or more nuclei by considering wave functions (  ) and symmetry restrictions.  Predicts bond orders, relative bond energies and magnetic properties.

9. 6/10/2015 Molecular Orbital Theory  Applicable to any molecule or ion. Note: Only diatomic molecules and ions were considered in this course.  Examples: N 2, O 2 –, Cl 2, NO +, etc.

10. 6/10/2015 Orbital Hybridization  Hybrid atomic orbitals (hao) are formed by combining some of the ground state atomic orbitals (ao) of an atom.  Hybrid atomic orbitals result in directional bonding.  Bond orders, bond lengths, polarity (dipole moment) and planarity are predicted.

11. 6/10/2015 Orbital Hybridization  This theory is most applicable to compounds containing carbon or nitrogen.  Examples C 2 H 6, C 3 H 4, C 2 H 5 NS, C 2 H 4 O, NF 3, etc.

12. 6/10/2015 Valence Bond Theory  This theory involves the hybridization of the central metal ion in a transition metal complex.  The formation of empty hybrid orbitals on the central metal ion enables a ligand to donate a pair of electrons to form a covalent bond with the ligand positioned in a definite geometry.

13. 6/10/2015 Valence Bond Theory  Geometry, magnetic properties and the possibility of color are predicted.  Examples [Cu(NH 3 ) 4 ] 2+, [Zn(OH) 4 ] 2–, [Cr(H 2 O) 6 ] 3+, [AgCl 2 ] –, etc.

14. 6/10/2015 Valence Shell Electron Pair Repulsion  By considering valence electrons and the effects of nonbonding electron pairs this theory accurately describes the geometry around the central atom in polyatomic ions and molecules.  Directly applicable to nonmetals.

15. 6/10/2015 Valence Shell Electron Pair Repulsion  Examples OF 2, ClF 3, SiH 4, ClF 4 –, etc.

16. 6/10/2015