![]() ![]() Conversely, if the electron is off to one side, in an anti-binding region, it actually adds to the repulsion between the two nuclei and helps push them away. For this to happen, the electron must be in a region of space which we call the binding region. But all of these valence-bond models, as they are generally called, are very limited in their applicability and predictive power, because they fail to recognize that distribution of the pooled valence electrons is governed by the totality of positive centers.Ĭhemical bonding occurs when the net attractive forces between an electron and two nuclei exceeds the electrostatic repulsion between the two nuclei. The more sophisticated hybridization model recognized that these orbitals will be modified by their interaction with other atoms. ![]() This is a big departure from the simple Lewis and VSEPR models that were based on the one-center orbitals of individual atoms. In its full development, molecular orbital theory involves a lot of complicated mathematics, but the fundamental ideas behind it are quite easily understood, and this is all we will try to accomplish in this lesson. The molecular orbital model is by far the most productive of the various models of chemical bonding, and serves as the basis for most quantiative calculations, including those that lead to many of the computer-generated images that you have seen elsewhere in these units. Construct a "molecular orbital diagram" of the kind shown in this lesson for a simple diatomic molecule, and indicate whether the molecule or its positive and negative ions should be stable.Define bond order, and state its significance.Describe the essential difference between a sigma and a pi molecular orbital.Explain how bonding and antibonding orbitals arise from atomic orbitals, and how they differ physically.In what fundamental way does the molecular orbital model differ from the other models of chemical bonding that have been described in these lessons?.Make sure you thoroughly understand the following essential ideas In this case, N22+ has a bond order of 4, while O2- has a bond order of 1.5.\) The species with the higher bond order is more stable. This difference is due to the different number of valence electrons in oxygen and nitrogen atoms, as well as the charges on the species. In N22+, there are 2 electrons in the π2p orbitals and no electrons in the π2p* orbital. In O2-, there are 4 electrons in the π2p orbitals and 1 electron in the π2p* orbital. The main difference between the orbital diagrams of O2- and N22+ is the number of electrons in the π2p and π2p* orbitals. How do the orbital diagram layouts differ? Why? N22+ has all electrons paired, so it is diamagnetic.ĭ. O2- has an unpaired electron in the π2p* orbital, so it is paramagnetic. The molecular orbital diagram for N22+ is as follows:ġs (2 electrons) -> 1s* (2 electrons) -> 2s (2 electrons) -> 2s* (2 electrons) -> 2p (4 electrons) -> π2p (2 electrons)īond Order = (Number of electrons in bonding orbitals - Number of electrons in antibonding orbitals) / 2 ![]() The molecular orbital diagram for O2- is as follows:ġs (2 electrons) -> 1s* (2 electrons) -> 2s (2 electrons) -> 2s* (2 electrons) -> 2p (6 electrons) -> π2p (4 electrons) -> π2p* (1 electron)įor N22+, we have 12 electrons (7 from each nitrogen atom and 2 fewer electrons due to the positive charge). Molecular orbital diagrams for O2- and N22+:įor O2-, we have 17 electrons (8 from each oxygen atom and 1 extra electron). ![]()
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