When applying MO theory to heteronuclear diatomic molecules, the atomic orbitals used may be of

When applying MO theory to heteronuclear diatomic molecules,...

Key Concepts

Molecular Orbital Theory

Molecular orbital theory explains how atomic orbitals combine to form molecular orbitals that extend over the entire molecule. This model helps in understanding the electronic structure of molecules by treating electrons as delocalized over the molecule rather than confined to individual atoms.

Linear Combination of Atomic Orbitals (LCAO)

The formation of molecular orbitals involves taking appropriate linear combinations of atomic orbitals. This approach helps describe both bonding and antibonding interactions, where the coefficients in the combination determine the contribution of each atomic orbital to the molecular orbital.

Energy Splitting in Heteronuclear Molecules

In heteronuclear molecules, the atomic orbitals have different intrinsic energies. When these orbitals combine, the resulting molecular orbitals are not symmetrically spaced between the original energies; instead, the lower-energy atomic orbital contributes more to the bonding orbital, lowering its energy further while the antibonding orbital is raised, often reflecting a closer energy alignment with the higher energy atomic orbital.

Bonding and Antibonding Orbitals

The linear combinations of atomic orbitals yield bonding orbitals, which have constructive interference (increased electron density between the nuclei and lower energy), and antibonding orbitals, which have destructive interference (a node between nuclei and higher energy). This distinction is crucial in determining the stability and reactivity of the molecule.

Orbital Symmetry and Shape

The shapes of the resulting molecular orbitals are directly influenced by the symmetry and shapes of the combining atomic orbitals. Even though the energy levels may shift due to differences in atomic orbital energies, the overall spatial distribution and nodal properties of the molecular orbitals are a hybridization of the original atomic orbitals' shapes.

Transcript

00:01 All right, in this question, we're going to be talking about molecular orbitals, specifically with heteronucleic diatomic molecules.

00:07 To start off, let's talk about what that means.

00:11 Heteronucleic means different nuclei, just means different atoms, so we don't have the same one.

00:16 Diatomic means we've got two, and molecule, hopefully you know what that means.

00:21 And so basically this means we've got two different atoms and they come together to form a molecule.

00:26 So it could be like no or like, i don't know, of or even nf, something really simple, but it's got two different atoms coming together to form a molecule.

00:38 So the question is asking about the energies of the molecular orbitals that are formed as a result.

00:44 And i was able to find a chart online showing the different energy levels.

00:49 So first thing to note is that these are the energies of the orbitals in the two separate atoms that are coming together.

00:57 So let's say we were talking about like nf, for example.

01:03 F is more, fluorine is more electronegative, nitrogen is less electronegative.

01:09 And since it's fluorine is more electronegative, the energy of its orbitals is going to be lower because it holds its electrons better, needs less energy to keep them there.

01:18 Nitrogen is a little bit less, it's a little bit weaker hold on its electrons, so it's going to need more energy to be there.

01:25 And when they come together, they're going to form molecular orbitals, which are totally new orbitals where the electrons reside, and that represents the bond.

01:34 And these pretty much always come in pairs of bonding and anti -bonding.

01:39 And the anti -bonding has a little star all the time.

01:42 And we always get this trend where the bonding orbital is lower than both of the energies of the atomic orbitals.

01:49 And the anti -bonding molecular orbital is actually higher in energy than both of the original orbital.

01:55 Atomic orbitals.

01:58 And so this happens even if they're the same.

02:01 It's just that the sort of difference in energy from both of these, if it's the same atom, it's going to be the same.

02:08 So let's say if it was like n2, for example, we'd have like our s orbital for both of them, and they would both be the same energy gap to get to the anti -bonding one and the same energy gap to get to the bonding one.

02:23 Let's say this is a sigma bonding and anti -bonding.

02:26 It's the same one.

02:27 In this case, we see that it's different because there's two different atoms involved.

02:33 All right.

02:34 So next we're going to talk about the shape of these molecular orbitals, and there's two types of shapes that we can get.

02:39 It's bonding and anti -bonding.

02:42 And so first up, we've got to figure out what kind of orbital we're taking into account here.

02:48 And if it's bonding, then they'll come together and kind of squish to become bigger.

02:51 If they're anti -bonding, they'll kind of have a rifting.

02:54 In between them.

02:55 I can talk a little bit about that.

02:57 So let's say we're working with s orbitals.

02:59 We've got two atoms.

03:02 They've got their s orbitals, which look like big spheres around the nucleus, which i made red.

03:06 When these guys come together, we're going to get something where we've got both of our nuclei, and we've got two options.

03:13 So first let's look at the bonding option where they come together.

03:18 It's just going to look bigger...

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