#C2 molecular orbital diagram how to#
The best way to learn how to draw MO diagrams is to work on practice problems. However, recall that the more electronegative atom will be lower on the diagram. Why does this difference exist?Ĭonstructing MO diagrams for heteronuclear molecules require the same 4 steps as above. In general, B 2, C 2, and N 2 have the MO diagram depicted on the left. (Such as H 2O, NH 3, and CH 4.) However, notice the difference between orbitals of homonuclear diatomics for elements with an atomic number less than or equal to 7 versus more than 7. Lower energy MOs are filled first, followed by consecutively increasing orbitals.īuilding Molecular Orbital Diagrams for Homonuclear and Heteronuclear Diatomic Moleculesĭue to symmetry of the molecule, homonuclear MO’s are less difficult to derive than heteronuclear molecules and polyatomic molecules. Electrons from the atomic orbitals are assigned molecular orbitals in accordance with the Pauli Exclusion Principle.These MO overlap with either a sigma or pi bond and are designated in bonding, nonbonding, or antibonding orbitals with respect to their phases. Overlapping atomic orbitals produce molecular orbitals located in the middle of the diagram.Individual atomic orbitals (AO) are arranged on the far left and far right of the diagram.The Y-axis of a MO diagram represents the total energy (not potential nor Gibbs Energy) of the orbitals.General Notes on Molecular Orbital Diagrams
A pi-bond is formed from a "sideways" overlap. Nodes are regions where the probability of finding an electron is ZERO.Ī sigma-bond is an "end-to-end" bond formed from symmetric atomic orbitals. It is important to notice that the phase signs do NOT symbolize charges. A node occurs if the phase signs change from (+) to (-) or vice versa. Phases are designated either (+) or (-) relative to their wave "up" or wave "down" displacements. Note how the bonding orbitals come together constructively, while the antibonding orbitals do not. "Bonding" orbitals are less energetic than antibonding atomic orbitals and are in-phase, as depicted in the figure below. Orbitals that are out-of-phase with one of another are "antibonding" orbitals because regions with dense electron probabilities do not merge which destabilizes the molecule. Molecules consisting of two non-identical atoms are said to be heteronuclear diatomic, such as: CO, NO, HF, and LiF. Molecules consisting of two identical atoms are said to be homonuclear diatomic, such as: H 2, N 2, O 2, and F 2. A MO is defined as the combination of atomic orbitals. The region an electron is most likely to be found in a molecule. These steps may then be extrapolated to construct more difficult polyatomic diagrams. The objective of this wiki is to provide readers with the fundamental steps in constructing simple homonuclear and heteronuclear diatomic molecular orbital diagrams. They also provide information in predicting a molecule’s electronic spectra and paramagnetism. MO diagrams predict physical and chemical properties of a molecule such as shape, bond energy, bond length and bond angle. The MO theory incorporates the wave character of electrons in developing MO diagrams. \)Īlthough VSEPR and the Valence Bond theory accurately predict bond properties, they fail to fully explain some molecules.
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