MO Theory: Heteronuclear Diatomic Molecules - Video Tutorials & Practice Problems
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Heteronuclear Diatomic Molecules are composed of 2 different elements bonded together.
Molecular Orbital Diagrams of Heteronuclear Diatomics
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concept
MO Theory: Heteronuclear Diatomic Molecules Concept 1
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Recall that a heteronuclear diatomic molecule is composed of 2 different elements bonded together, and we're gonna say here that the less electronegative element determines which molecular orbital will be used. And recall that electronegativity increases as you move to the top right corner of the periodic table. Remember, fluorine is the most electronegative element with a value of 4 point o. Now we're gonna say here that when it comes to displaying these molecular orbitals or these molecular orbital diagrams, the more electronegative element within the heteronuclear diatomic molecule possesses atomic orbitals that are lower in energy. So here if we take a look, we have molecular orbital diagrams for hydrogen to helium, for lithium to nitrogen, and from oxygen to neon. If you watch my videos on molecular orbital theory, you're kind of familiar with these displays. Now if you notice, you can see here that this 2 s atomic orbital is higher in energy than this one. This one's lower down. That must mean that let's say we're combining we're comparing carbon to nitrogen. Carbon is less electronegative than nitrogen. Since nitrogen is more electronegative, it would be here on this side and carbon will be here on this side. And since nitrogen is more electronegative, that explains why its atomic orbitals are lower in energy. See here, its 2p orbitals are also lower in energy, carbons are higher in energy. And then here, if we look at oxygen to neon, same thing. This 2 s orbital, atomic orbital is higher in energy than this one, meaning the left side is involved with an element that has less electronegative. So for example, maybe we have here oxygen versus fluorine. Okay? So keep in mind that electronegativity helps us determine which molecular orbital diagram to use and also it helps us to see the differences in energy for our atomic orbitals. Now just remember that the higher your electronegativity, then the electrons will be closer to the nucleus, so they're more tightly bound to the nucleus. Okay? What effect can this have on our shell number here? So here our electrons are being pulled closer and closer to the nucleus since electron activity is increasing. This we'll see a lot of the times with lower numbered shell elements such as fluorine. So here we have a lower shell number. Alright. So keep in mind these fundamental ideas when we're talking about heteronuclear diatomic molecules and MO theory.
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example
MO Theory: Heteronuclear Diatomic Molecules Example 1
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Construct the molecular orbital diagram for the carbon monoxide molecule, so c o. Now here we're gonna determine the right molecular orbital diagram. Carbon is less electronegative than oxygen, so we're gonna use the molecular orbital diagram for carbon. So we use this middle one here. Now remember that the more electronegative element has lower energy in terms of its atomic orbitals. So oxygen will represent this side and carbon represent this side. Now in terms of number of valence electrons, we're going to say here that carbon is in group 4 a, so it has 4 valence electrons or valence electrons. So it'd be 1 up, 1 down, and then up, up. Oxygen is in group 6 a, so it has 6 valence electrons. So 1, 2, 3, 4, 5, and then 6. We now pull together our electrons from the atomic orbitals and put them into the molecular orbitals. So it'd be up, down, up, down. Now we have a total of how many electrons here? Six electrons that we basically need to put into these remaining molecular orbitals. So it'd be up, up, down, down, and then we need 2 more, up, down. So this would represent the filled in molecular orbital diagram for carbon monoxide. We'd come down here and we'd fill it in. So we're gonna say we have 2 of sigma 2 s, 2 of sigma star 2 s, we see that we have 4 4 pi 2p, and then finally we'd have 2 in the sigma 2p. So this would be all the electrons that we have to fill in this electron, configuration for carbon monoxide. Now here, these would have nothing in them so you could in theory, if you want, just remove them from this because there'd be 0 in here and 0 in here. So we have our molecular orbital diagram above and this would be the completed electron configuration using that molecular orbital diagram for carbon monoxide.
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Problem
Problem
Apply Molecular Orbital Theory to determine the MO orbital diagram for the CF+ ion.
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Problem
Problem
Using a MO diagram, write the electron configuration for the BN molecule?