A method of studying bonds between atoms in which electrons' motions are defined as being all around the molecule, though influenced by nuclei.

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How are the hydrogens attached to the nitrogen atom in the ammonium ion?

Naively attaching hydrogens to a nitrogen atom's electron orbitals results in a picture like this: However, there are two problems with this drawing that I can see. First, I have heard that the ...
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18 views

Determining the type of electrocyclic via MO theory

I have been working on this particular problem for a while now to determine how this particular reaction plays out. I think it is a a thermo electrocyclic ring transformation involving 6 pi ...
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57 views

Ordinary differential equation for molecule collision

My knowledge in 0 in chemistry. But, I have a good background in mathematics and computer programming. I have planed to simulate the collision of two simple molecules $\ce{Br2}$ and $\ce{H2}$ just ...
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32 views

Why HF is said to be formed from H-1s and F-2pz overlap?

According to Wikipedia, HF is formed by the interaction between hydrogen's $1s$ orbital and fluoride’s $2p_z$ orbital: In hydrogen fluoride HF overlap between the H 1s and F 2s orbitals is ...
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17 views

Can you deduce unsaturated fatty acid structure from orbital hybridisation theory?

In biology class we have seen how an unsaturated fatty acid has a double carbon bond which makes the molecule bend. In chemistry class we have seen orbital hybridisation theory and as an exercise I ...
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95 views

Why does AsH5 not exist?

Why does $\ce{AsH5}$ not exist? Is it because the s-orbital of H doesn't and can't overlap with the d-orbital of As after As makes $\rm sp^{3}d$ hybridization?Theoretically the bond can occur because ...
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1answer
43 views

How to compare the energies of sigma and pi bonds in molecular orbitals of diatomic heteronuclear species?

There is a rule for diatomic homo-nuclear species that says that if $Z<8$ then $$E(\sigma_{2p})>[E(\pi_{2p_y})=E(\pi_{2p_z})]$$ and the inverse if $Z\geq8$ and in both case we have energy of ...
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40 views

Why is conjugation not possible if there is not present alternate $\pi$ molecules according to MO theory?

I was reading this page at Chemwiki; there they were discussing conjugated-$\pi$ bond. In order to show that conjugation requires alternate double bonding, they cited the example of ...
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109 views

Jahn-Teller Distortions in Square Planar Complexes?

A Jahn-Teller distortion is predicted whenever a non-linear symmetric molecule has degenerate orbitals and has unequal electron occupation in those degenerate orbitals. Of course this most often is ...
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1answer
35 views

Is it possible to have accumulation of electron density in the inter-nuclear region even if the overlap integral is zero?

Recap: Lately, I've been studying Hückel theory where I learned about the approximation of neglecting all overlaps and making overlap matrix an identity matrix that is $S_{AB}= 0\;_; \;S_{AA}= 1$ or ...
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2answers
121 views

How can off-diagonal Hamiltonian matrix elements be nonzero when the overlap matrix is diagonal?

While studying about Hückel theory, I got accustomed to the approximation of making the overlap matrix an identity matrix; that is making the off-diagonal elements zero as $S_{AB}= S_{BA}= 0\;;$ this ...
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1answer
57 views

What is the reason behind neglecting & putting the overlap integrals $0$ in Simple Hückel Theory?

This is an excerpt about Simple Hückel Theory from Elements of Physical Chemistry by Peter Atkins: The first step that Hückel took was to ignore the $\sigma$-bonding framework and focus solely on ...
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1answer
140 views

How to determine gerade & ungerade symmetry of a MO orbital?

J.D.Lee writes in his book Concise Inorganic Chemistry: [...] An alternative method for determining the symmetry of the molecular orbital is to rotate the orbital about the line joining the two ...
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1answer
61 views

'In MO theory, electrons are treated as spreading throughout the entire molecule'- isn't it exhibited in VB theory also?

First statement: In the molecular orbital theory, the valency electrons are considered to be associated with all the nuclei in the molecule. - Concise Inorganic Chemistry by J.D.Lee. Second ...
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1answer
89 views

Why does the PH3 geometry deviate more from the trigonal planar one, than does NH3?

$\ce{PH3}$ has a more bent structure than $\ce{NH3}$. The HOMO-LUMO gap for $\ce{PH3}$ is smaller than for $\ce{NH3}$, and so the distortion from the trigonal planar geometry is said to be larger. ...
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33 views

Successful predictions of MO software?

There have been many successful predictions of MO software. Is there a website or journal dedicated to recording them all?
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42 views

Molecular Orbital Diagram for dioxygen

In the MO diagram for $O_{2}$ : Shouldn't there be 3 different $3\sigma_{g}$ Bonding MO's as each p orbital can form a $\sigma_{g}$ Bonding MO along its respective axes? In which case the ...
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90 views

How derive g and u symmetry labels for orbitals?

When asked whether a molecule has an inversion center, we "invert" the coordinates of all atoms; i.e. move each atom from its position through the center of symmetry and to a new position equidistant ...
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45 views

What will occur after excitation of electron from HOMO to LUMO?

After an electron absorbs the sufficient energy it will get excited from the HOMO to LUMO state. Does this mean that after excitation, molecules will be $50\%$ with LUMO (have one electron) and ...
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53 views

Transition of electron from HOMO to LUMO?

Molecules usually have certain number of (doubly) occupied molecular orbitals and an infinite number of unoccupied molecular orbitals but the probability of electron makes the orbitals shapes so, how ...
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1answer
192 views

Why does the mixing of sigma 2s and 2p orbitals lower the energy of the sigma 2s orbital and raise the energy of the sigma 2p orbital?

My general chemistry textbook (General Chemistry Principles and Modern Applications, Tenth Edition) says that for bonding in diatomic molecules with Z ≤ 7, orbital mixing occurs between the ...
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1answer
47 views

How does one calculate chemical shift in a gauge independent manner?

The literature on ab initio calculations of chemical shift in NMR experiments usually provide Lamb's and Ramsey's formulae as the solution. Yet the expressions explicitly depend on vector potential ...
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1answer
177 views

How to determine VSEPR shape from molecular orbital theory?

The molecule $\ce{[PdCl4]^2-}$ is diamagnetic. So since $\ce{Pd}$ is $\mathrm{d^8}$, and the oxidation number is $+2$, that means, there are two lone pairs, so the molecule is $\ce{AX4E2}$, making it ...
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55 views

MO shapes for dx2-y2 sigma bond

How do the Bonding and Anti-bonding MOs of dx2-y2 sigma bonding with another dx2-y2 look like ? I mean to ask that if the sigma bond is along the x-axis then is the shape of the lobes along y-axis ...
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17 views

In molecular orbital theory when two different atoms are combined, how do you tell which one is higher energy? [duplicate]

So in the picture above, see that there is an Atom A and Atom B and they combine. Notice that Atom A is higher in energy than Atom B (as indicated by how the 2s and 2p lines are drawn higher). ...
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1answer
48 views

Discrepancy in MO diagrams for Period 2 homonuclear diatomics

I've recently noticed that different sources on the internet and in books have different ideas of whcih atomic orbital influences which molecular orbital. In the diagram, where the lines connect the ...
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1answer
70 views

Point Groups and MO Theory

I am a little confused about how point groups give information about MO of polyatomic molecules. Is it true that all molecules of a given point group such as, $\mathrm{C_{2v}}$, will have the same MO ...
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1answer
51 views

How can we find the eV value of molecular orbital diagrams for a given atom?

It seems like sometimes the electron volt value of the molecular orbital is given but most of the time it just shows relative values of s p d orbitals. Is there some lookup table for such values?
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2answers
97 views

Hybrid orbitals forming molecular orbitals

My teacher showed me this diagram on how the hybrid orbitals of two atoms combine to form molecular orbitals. I was confused by this because I thought that VB and MO theories were two separate ...
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1answer
34 views

Closed shell molecules can have degenerate states?

I read a paper which said that $\ce{CO2}$ despite having orbital degeneracy is stable and not subject to the Jahn-Teller effect because it is a linear molecule. But $\ce{CO2}$ is a closed shell ...
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1answer
51 views

Orbital conservation in Molecular orbital theory

MOT is really confusing me. I was taught that the no. of orbitals remains conserved.That means, the number of atomic orbitals used is equal in number to the molecular orbitals formed. But how is it ...
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52 views

Frost circle method for determining aromaticity

Can the 'Frost Circle' method for determining aromaticity be used for bicyclic or multicyclic compounds???
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32 views

Why does ethene only have 1 pi bonding molecular orbital?

I was wondering why ethene has only 1 pi molecular orbital, because other molecules such as oxygen has 2 electron pairs in each pi orbital. I think it may be to do with how the carbon on ethene is sp2 ...
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160 views

How is the Felkin-Anh model of stereoinduction correctly explained with MO theory?

One method to predict stereoinduction in asymmetric reactions is the Felkin-Anh model (derived from the more basic Cram model) that applies to nucleophile attacks on α-chiral aldehydes. In a ...
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1answer
176 views

What's the difference between HOMO-LUMO and valence-conduction bands?

From Wikipedia: Roughly, the HOMO level is to organic semiconductors what the valence band maximum is to inorganic semiconductors and quantum dots. The same analogy exists between the LUMO ...
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53 views

How to determine bond order for special cases?

In AP Chemistry, we learned two ways to determine bond order. The first method is: Bond order = (bonding electrons - antibonding electrons)/2. The second method is: number of bonds / number of bond ...
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1answer
216 views

How can the intense color of potassium permanganate be explained with molecular orbital theory?

In the permanganate ion, manganese is in the $+7$ oxidation state, therefore it is a $\ce{d^0}$ ion. $\ce{d^0}$ and $\ce{d^1^0}$ ions don't absorb visible spectrum radiation because there are no ...
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2answers
118 views

Formation of Bonding and Anti-bonding Molecular Orbitals

If two orbitals combine in-phase, a bonding molecular orbital is formed. When they combine out-of-phase, an anti-bonding molecular orbital is formed. For a single molecule, how are both orbitals ...
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1answer
72 views

Physical Meaning of the Difference between MO and VB Wave Function of H2?

What would be the physical meaning of the difference between the MO wave function and VB wave function of $\ce{H2}$?
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677 views

carbon monoxide and orbital hybridization

If we look at CO in terms of orbital hybridization, we conclude that both atoms are sp hybridized since they share a triple bond. My question: When creating those hybrid orbitals, those ought to be ...
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1answer
107 views

Alternative Program for Orbital Population Analysis

Gaussian has Orbital-by-Orbital Population Analysis. From the manual: ...
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1answer
119 views

Molecular orbital destabilization energy

Shouldn't the antibonding orbital be destabilized more than the bonding orbital is stabilized? In other words, do you agree with the bolded caption in my textbook? Also, is it true that for ...
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1answer
60 views

Creating Pi Molecular Orbitals from P Atomic Orbitals

As shown in the image, we have two free p orbitals in ethene but we need two p orbitals each for the bonding and anti-bonding orbital. That is a total of four. What is the concept behind this?
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1answer
121 views

Hybridization, MOT and Paramagnetism

In what way can hybridization or molecular orbital theory be used to explain paramagnetism? For instance, when something is hybridized to make enough bonding electrons, do all the electrons end up ...
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1answer
166 views

How can the gauche-effect be explained?

Generally, anti-conformations are more stable. But in the case of 2-fluoroethanol, the gauche confirmation is more stable. It's given in March's advanced organic chemistry book that intramolecular ...
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1answer
107 views

How is a molecular orbital a 'quantum superposition' of the atomic orbitals?

Let me quote from Feynman's lectures the concept of superposition: (1)The probability of an event in an ideal experiment is given by the square of the absolute value of a complex number $ϕ$ which ...
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225 views

What do positive, negative and zero overlap of atomic orbitals mean?

I am confused about positive, negative and zero overlaps. Do they represent the extent of overlap or are they related to the bonding and anti-bonding orbitals as described in Molecular Orbital ...
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1answer
53 views

Stereochemistry of product in Diels-Alder reaction

I have a few questions on this problem I solved: 1) Why does carbon "b" on methyl vinyl ketone attack carbon "5" on the lactone? Why not carbon "2"? 2) The answer key says that the end product ...
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1answer
99 views

Axial vs equatorial attack of Grignard reagent on dioxan-5-one and dithian-5-one

How to account for the diastereoselectivety (axial vs equatorial attack) of these reactions?
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3answers
222 views

How is hyperconjugation into antibonding orbitals stabilizing?

So I learned that hyperconjugation is electron delocalization from a $\ce{C-H}$ $\unicode[Times]{x3C3}$ bond into an empty p orbital (on a carbocation for example) or an antibonding orbital. I get how ...