All Questions
Tagged with molecular-orbitals or molecular-orbital-theory
792 questions
4
votes
2
answers
310
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MO diagram when three orbitals of the same symmetry is allowed to mix
How exactly should we combine three orbitals when we have three orbitals that are of correct symmetry to interact?
Take $\ce{H2O}$ for example. $\mathrm{2s},$ $\mathrm{2p}_z$ and the $A_1$ group $(\ce{...
- 61
2
votes
2
answers
172
views
Insight into covalent bonds from electrostatic perspective
I try to understand, from the electromagnetic side only, how the molecule could be more stable than each atom, and concluded that it could not. Where is my mistake?
Here is an illustration :
By using ...
4
votes
0
answers
93
views
Symmetry Operation on Product of Functions
In regards to direct product representations, I'm trying to find a proof for:
$R(X_iY_j)=R(X_i)R(Y_j)$
Where $R$ is a symmetry operation of a group and $X_i$ and $Y_j$ are members of different basis ...
- 41
1
vote
0
answers
937
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Comparison between Molecular Orbital Theory and Valence Bond Theory
I have been reading about introductory Molecular Orbital Theory lately. Till now, I have used Valence Bond Theory to evaluate bonding. I have a few questions about it:-
In VBT, we used the idea that ...
- 169
4
votes
1
answer
106
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Can we relate approximate Hartree-Fock orbitals to true solutions in the basis-set limit?
Assume that we've "solved" the RHF Hartree-Fock equations in some finite basis, that is, we have arrived at a self-consistent set of coefficients $c_{\mu{}i}$ such that each spatial ...
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-4
votes
1
answer
176
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Do higher orbitals have more energy or less energy? [duplicate]
I've recently learned that as an orbital gets larger, its energy gets closer to 0. Before this, I learned that when an electron moves down an orbital it releases the energy difference between those ...
- 101
1
vote
1
answer
1k
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Why do PES graphs list 4s after 3d? [duplicate]
Coming straight off of some electron configuration worksheets, our teacher started to teach us how to read photoelectron spectroscopy (PES) graphs and I'm having a bit of trouble with the two.
During ...
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4
votes
2
answers
6k
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Why is the first ionization enthalpy of molecular O2 less than atomic O?
A cousin of mine asked for my help to answer one of his homework questions. It stated-
Explain why- The first ionization energy of molecular oxygen $\ce{O2}$ ($\pu{1175 kJ mol-1}$), is lesser than ...
- 1,189
5
votes
1
answer
2k
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Is there s-character in the HOMO of dinitrogen?
State true or false:
The highest occupied molecular orbital in nitrogen molecule has no s-character.
The answer given is that this false. Why is it so?
The highest occupied molecular orbital in $\ce{...
- 133
0
votes
1
answer
184
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Jahn Teller Effect on Metal Complexes
I've been learning how the Jahn Teller Distortion effects the orbitals in Metal complexes and how the splitting of eg and t2g orbitals happens.
But the book mentions that the effect is strong for ...
- 748
2
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0
answers
1k
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Why is it rational that salt-bridges (in proteins) are described as a combination of H-bond and ionic bond?
This is a fundamental question that came to me as I was trying to draw the electrostatic attraction between Aspartate (D) and lysine (K). I have always considered the charge on nitrogen, in the lysine ...
- 928
2
votes
0
answers
29
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Is there any way we can arrive at a general principle of magnetic character based on the bond order (ie; fractional or integral)?
So, after going through two assignments on Chemical Bonding and the Molecular Orbital theory, I saw that in most of the problems where we were asked about the magnetic character of a molecule (...
0
votes
0
answers
612
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Hybridization state of oxygen in carbonyl sulfide (COS) [duplicate]
I've been scratching my head on this one for awhile here. In a carbonyl sulfide (COS) molecule, what is the hybridization state of oxygen?
Carbonyl sulfide is composed of a single carbon atom double ...
- 23
4
votes
1
answer
2k
views
Book Recommendation for Molecular Orbital Theory [duplicate]
I posting my question here since I have seen similar questions but I haven't found the specific answer I am searching for. I am seeking textbook recommendations on Molecular Orbital Theory with ...
- 167
1
vote
0
answers
692
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How is Pi antibonding orbital more polar than Pi bonding orbital?
While reading about the solvent effect on electronic transition in ESR spectroscopy, I found it written somewhere that the pi anti-bonding orbitals are more polar compared to pi bonding orbitals.
Can ...
- 307
1
vote
1
answer
146
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Chemical reaction of radicals with different multiplicity
I am studying the chemical reaction of radicals by computational chemistry software.
I just want to know what is the rules for multiplicity.
I have two radicals for which, the ground state of one is a ...
- 11
5
votes
1
answer
465
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Intuitive Explanation for why more negative charge on ligand does not imply more splitting effect?
I have studied coordination chemistry as part of my school curriculum and we covered Crystal Field Theory as our final theory, and the book says that Ligand Field Theory and Molecular Orbital Theory ...
11
votes
2
answers
942
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How is Bent's rule consistent with LCAO MO theory?
Bent's Rule states that $s$ orbitals on a central atom participate contribute more to molecular orbitals directed towards more electropositive ligands. (For a longer explanation, see this question and ...
- 10.4k
1
vote
2
answers
105
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Average energy concept
Problem
When the number of electrons in bonding molecular orbitals is equal to number of electrons in anti-bonding molecular orbitals bond cannot be formed between two atoms because
A) Bonding effect ...
- 51
-4
votes
1
answer
440
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molecular orbital theory explaining molecular orbitals [closed]
i am a high school student,,and i am confused in molecular orbital theory,,,my confusion is that how bonding and non bonding orbitals are formed at the same time my teacher taught me that the two wave ...
- 29
2
votes
1
answer
6k
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What is the structure of CF3 radical? [duplicate]
In the class, I was told that $\ce{H3C^.}$ has a trigonal planar structure with the unpaired electron in $\mathrm{2p_z}$ orbital. But $\ce{H3C -}$ has a trigonal pyramidal structure.
But why does ...
- 185
7
votes
1
answer
2k
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What is the shape of [Cr(NO)₄]?
I was learning about crystal field theory recently. I am quite confused about predicting the shape of $\ce{[Cr(NO)4]}$ complex because I am not able to conclude whether it will be square planar or ...
- 807
2
votes
0
answers
96
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Can one describe the bonding of Na to F in terms of molecular orbital theory? What about valence bond theory?
I would kindly appreciate an explanation in terms of the two accepted quantum mechanical theories -valence bond & molecular orbitals- for the electronic energy level structure in natrium fluoride $...
- 217
4
votes
0
answers
476
views
Symmetry Adapted molecular orbitals of Formaldehyde
I am currently trying to find the Symmetry Adapted linear Combinations (SALCs) of Formaldehyde $\ce{H2C=O}$, and use the 1s orbitals on the hydrogen atoms, and 2s, 2px, 2py and 2pz orbitals on the ...
4
votes
0
answers
367
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Molecular orbital diagram of CO and charge localisation
MO diagram of CO
My question concerns the interpretation of the Molecular Orbital of CO. I think I find it clear how you build it but I have some concerns about how you rationalize it.
Particularly, ...
- 93
3
votes
0
answers
135
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(Mis)understanding on MOT
In VBT, one can understand the example of hydrogen like this - Two hydrogen atoms come closer to each other, and their orbitals overlap, stabilize, and ultimately result in a bond. This is not too ...
-1
votes
1
answer
818
views
What is the maximum number of hybrid orbitals an atom can have? [closed]
What is the maximum number of hybrid orbitals and atom can have? It is usually seen that an atom does not have more than 6 hybrid orbitals. Why is it so?
3
votes
1
answer
138
views
Do SALC-AOs really belong to their symmetry species?
I'm working through a molecular symmetry textbook and something keeps nagging at me. If I derive the SALC-AOs for NH3 (using the projection operator method), I'll get
A1: $ \frac{1}{\sqrt{3}}(\...
- 33
4
votes
1
answer
674
views
Overlap integrals in Hückel theory
In Hückel theory we are only interested in π systems, where $\mathrm p_z$ orbitals overlap. One of the approximations in Hückel theory is that the overlapping $\mathrm p_z$ orbitals are orthonormal:
$...
- 302
4
votes
1
answer
1k
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How do we obtain the π molecular orbitals for allene via Hückel theory?
For a conjugated system, for instance 1,3-butadiene, we can try to obtain the π molecular orbital energies and wavefunctions via Hückel theory. In our given molecule, there are 4 interacting Pz ...
- 302
2
votes
0
answers
48
views
Focusing on HOMO when discussing thermal electrocyclic reactions
When taking into consideration the outcome of a thermal electrocyclic reaction, why do we focus specifically on the HOMO of the conjugated polyene? Why does it seemingly have the highest contribution ...
0
votes
0
answers
102
views
Precise definition of cylindrically symmetry in MO theory?
I was watching an MIT OpenCourseWare lecture on MO theory which mentioned that $\sigma$ orbitals are "cylindrically symmetrical." I was a bit confused, because I was under the assumption that the ...
- 201
9
votes
1
answer
138
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Computing energy of Gaussian basis set
I'd like to compute the decay rate using
$$ \Gamma = 2\pi \ | \langle ab|V|cd \rangle|^2 \delta\ (\epsilon_\mathrm{f}-\epsilon_\mathrm{i}), \tag{1}$$
where $a,$ $b,$ $c,$ $d$ are the MOs, $V$ is the ...
- 123
4
votes
0
answers
760
views
Molecular orbital diagram for I₃⁺ cation
Do I need to go through the whole process of reducible representations/projection operator method to come up with the bent SALCs for the $\ce{[I3]+}$ molecule? Or is it simpler than that?
- 347
1
vote
0
answers
378
views
Breaking bonds with magnetic fields
I was wondering if we could break a bond by applying a big magnetic field on a molecule. The magnetic would just cause the spin of cores of the atoms making the molecule to be aligned , raising the ...
- 123
1
vote
1
answer
60
views
Why does a bonding molecular orbtial increase stability? [duplicate]
When two atomic orbitals come together, they fuse to form a molecular orbital. There is a large probability that the electrons will spend time between the nuclei. This will reduce the nuclei - nuclei ...
- 1,582
2
votes
1
answer
121
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Connection between irreducible representations and electronic states in diatomic molecules
I am trying to understand the connection between irreducible representations and molecular electronic states.
To explain the problem: I found some potential energy curves (PECs) for $\ce{N2+}$ in the ...
- 255
4
votes
1
answer
328
views
How are molecular orbitals obtained in quantum chemistry?
When trying to solve for a molecule's molecular orbitals, we start off with the total molecular hamiltonian. However, given the difficulty of solving the Schrödinger Equation for this complicated ...
- 302
3
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0
answers
57
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Why is 4-t-butyl aci-nitro cyclohexane stable whereas aci-nitro cyclohexane is not?
During my PhD, about fifty years ago, I had reason to use 4-t-butyl aci-nitro cyclohexane and found it to be remarkably stable. Usually aci- nitro compounds revert to nitro compounds very quickly ...
0
votes
1
answer
84
views
Molecular antibonding orbitals energy
When we heat hydrogen the energy of the molecular orbital of H2(1s) is increased .What happens to the energy of the antibonding molecular energy of hydrogen(1s*)?
- 123
2
votes
1
answer
248
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Projection Operator Method on Cl4+
I am not quite sure how to start on 1b.We are given 2 diagrams but I am not sure how to use the second one in the question, or if we have to. I got the point group for Cl4+ to be (D2h) however, but ...
- 71
8
votes
1
answer
978
views
Does the hybridization of sp3d2 type exist?
Is the hybridization of $\ce{XeOF4}$ $\mathrm{sp^2}$ rather than $\mathrm{sp^3d^2}$, because the latter type of hybridization does not exist?
Every answer in the Quora thread "How can we find the ...
6
votes
1
answer
3k
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Why is the carbon monoxide triple bond stronger than the nitrogen-nitrogen triple bond?
The $\ce{CO}$ triple bond has a bond enthalpy of 1072 kJ/mol while the $\ce{N2}$ triple bond has a bond enthalpy of 945 kJ/mol, at least according to my source. The molecules are isoelectronic, so I ...
- 509
1
vote
0
answers
990
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Why is the top SN2 reaction faster? (Molecular Orbital Theory)
I'm having trouble understanding why the top SN2 reaction proceeds faster. I know that benzylic and allylic halides react faster in SN2 reactions than non-conjugated halides. I think it's because the ...
1
vote
1
answer
1k
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How can ionic bonding in lanthanides occur without valence orbitals available for overlap?
I've recently been taught that the 4f orbitals in lanthanides are "core-like", supposedly meaning they have radius smaller than the 4d orbitals, therefore they are not available on the outside of the ...
- 33
4
votes
0
answers
482
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What exactly are the frontier orbitals in diradical species like O2?
I read about frontier orbitals, namely HOMO, LUMO. But what's exactly HOMO/LUMO? I know HOMO stands for highest occupied molecular orbital and LUMO stands for lowest unoccupied molecular orbital.
But ...
- 1,350
6
votes
1
answer
311
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What can we learn from the energies of molecular orbitals?
Molecular orbital theory is successful in calculating the structure of molecules (minimizing the total energy with respect to atomic positions). The solutions of an MO calculation are useful in ...
- 42.3k
1
vote
0
answers
28
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CO2 dynamics-vector correlations [closed]
I would like to ask if anyone has any information (schematic diagram)of vector correlations for CO2 molecule. (Is it bending in the excited state with μ in plane? How CO fragment can be ejected after ...
- 11
4
votes
1
answer
387
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For molecular orbitals, how is an energy of zero set or defined?
When labeling the energies of molecular orbitals, often some anti-bonding MOs are shown with a positive energy. For example, MolCalc has the following energies for methane (the anti-bonding MO #8 at +...
- 42.3k
1
vote
0
answers
67
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Why does ψ^2 ( square of orbital wave function ψ) give the probability of an electron in a given region? [duplicate]
Today I was introduced to the Orbital Wave Function for electrons.
$\Psi$ is a mathematical function for coordinate of electrons and has no physical meaning.
But $\Psi^2$ gives probability of an ...
