Questions tagged [molecular-orbital-theory]

Use of molecular orbital (MO) theory allows for an understanding of the observed properties (shape, reactivity) of molecules. The tag should be applied to all questions related to MO theory, from questions about the qualitative use of the theory to questions about the underlying quantum mechanics and applications in computational chemistry.

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Molecular orbital theory vs Hybridisation theory

In molecular orbital theory, do the atomic orbitals undergo hybridisation or do the atomic orbitals just overlap with each other to form molecular orbitals. What I'm confused about is the difference ...
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What is the physical basis of the reversal of the order of filling due to s-p mixing? [closed]

what exact changes does sp mixing bring about to molecular structures which leads to the 𝝅2px=𝝅2py orbital being filled before the σ2pz orbital?
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Does (BeCl2)n have 3c - 4e- bonding or not?

The title really explains what the issue is here. I would think that it has multicenter bonding akin to $(\ce{BeH2})_n$ polymer because they are pretty much iso-structural (although it shouldn't have $...
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How can 2 molecular orbitals form simultaneously? [duplicate]

I understand (for example in the case of H2) that two s orbitals produce through constructive interference a bonding orbital and that the out of phase combination of two s orbitals leads to ...
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2answers
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Is strength of pi bonds greater than sigma bond of nitrogen molecule?

I am referring to molecular orbital (MO) theory. In the nitrogen molecule (and elements of lower atomic number) $\textrm{sp}$ mixing occurs and the sigma orbital set is raised above the pi orbital set....
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Computational determination of the diagram of molecular orbitals of a polyatomic chemical species

A diagram of molecular orbitals for $\ce{H2O}$ would be as follows: The above diagram has been constructed qualitatively following the steps that I have been instructed in various classes on this ...
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Question regarding conflicting results of checking the electron-preciseness of isoelectronic species via NBO and EHM calculations

It is well known that the tert-butyl cation's empty 2p orbital on the central carbon is stabilised by hyperconjugation from neighboring C-H bonds. This would mean that the central 2p "lone pair&...
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1answer
155 views

What is the correct molecular orbital diagram for the d orbitals in platinum for the tetraammineplatinum(II) complex?

I am trying to construct the diagram of $\mathrm{d}$ orbitals in the tetraammineplatinum(II) complex. According to the angular overlap model, $\mathrm{d}$ orbitals are going to look like those in the ...
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Molecular orbitals energy under pressure

Suppose we have a hydrogen molecule $\ce{H2}.$ At room temperature the average distance of the nuclei is $r_0$ (without applying pressure). If we put $n$ hydrogen molecules in a box with volume $V_\...
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Construction of the molecular orbital diagram for a species M4

I need to construct the molecular orbital diagram for the hypothetical species ${Li_4}$, which has the following geometrical arrangement: The first step is to identify the point symmetry group. In ...
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51 views

Why d and s orbitals overlap even when there is considerable difference in their energies?

In my grade 11 chemistry NCERT textbook, its written that hybridization happens when orbitals of almost same energy overlaps. But S orbital and D orbital have significant difference in their energies. ...
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First ionization energy and electron gain enthalpy of dihydrogen / stability comparison of dihydrogen ions [duplicate]

Subset of: How can antibonding orbitals be more antibonding than bonding orbitals are bonding? Stability of $\ce{H2^{-}}<\ce{H2^{+}}<\ce{H2}$ Stability of $\ce{N2^{-}}<\ce{N2^{+}}<\ce{N2}...
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How can orbitals of Hydrogen and Chlorine atom combine to form molecular orbitals of Hydrogen Chloride? [closed]

Linear combination of atomic orbitals (LCAO) states that orbitals can only combine if the energies and shape of the orbitals are same. $3p$ orbital of Chlorine and $1s$ orbital of Hydrogen are the ...
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Spin Multiplicities of Ions

The multiplicity is fundamentally defined as $2S + 1$ where $S$ is the total spin. From what I understand, the multiplicity corresponds with the number of unpaired/paired electrons. For example, in ...
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molecular orbital theory and crystal field theory confusions

I am a high school student and I am very confused in Molecular orbital theory, it says that when two orbitals overlaps in the same phase, they form antibonding orbitals and when they overlap in ...
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Explanation of the trans-effect (thermodynamic and kinetic) for octahedral transition metal complexes

The thermodynamic trans effect refers to the ground state weakening of the metal-ligand bond in a complex by a ligand trans to it. The kinetic trans effect is the lablisation of a ligand in a complex ...
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1answer
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What is the LUMO of a molecule with an alkene and a carbonyl?

In a molecule that has both an alkene (C=C) and carbonyl (C=O) that are NOT conjugated, such as pent-4-en-2-one, how do you determine which π* anti-bonding orbital is the LUMO? Essentially, I'm trying ...
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Is an element's “atomic electron configuration” EXACTLY equal to the term with the largest coefficient in the CI series of the neutral atom?

For atoms and molecules with more than one electron, the wavefunction cannot be written as a single Slater determinant, so the ground-state configuration of (the atom or molecule in question) is ...
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How do atomic orbitals interfere both constructively AND destructively to give two molecular orbitals?

I am an organic chemistry student learning how atomic orbitals interfere to give rise to molecular obitals. The image below suggests that each of the hydrogens' atomic orbitals interfere both ...
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1answer
310 views

Why is a sodium chloride molecule stable?

The ionization energy of sodium is $\pu{5.139eV}$. This is the energy absorbed when a neutral sodium atom is stripped of its outermost electron. The electron affinity of chlorine is $\pu{3.62eV}$. ...
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Relation between the number of hybridised orbitals and the number of sigma bonds

March's Advanced Organic Chemistry (8th Ed.), has in its first chapter several tantalizing statements of the following variety; Boron has only three valence electrons available to form bonds, hence ...
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A contradiction in the nucleophilic attack of hydride ion based on charge densities

On page 130 of Organic Chemistry by Clayden, it is stated that Nucleophilic attack by the hydride ion, $\ce{H-}$, is an almost unknown reaction. This species, which is present in the salt sodium ...
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Orbital Interaction for electrophile and nucleophile

Clearly the above diagrams depict the interaction between empty orbital of electrophile with filled orbital of nucleophile. We may assume that the HOMO of nucleophile being more electronegative will ...
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1answer
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Why does STED microscopy cause photodamage?

STED (stimulated emission depletion) microscopy is a technique which enables sub-diffraction limit of light imaging. The depletion laser is at 775nm, and about 500 mW, concentrated for a short ...
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What makes up the conduction band?

Prologue/Rant about online classes We have been taught the electron sea model to explain metallic bonding and conduction of electricity by metals. Then out of the blue, the band theory was introduced, ...
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Molecular Orbital Diagram

Chemists have revealed that $1 \lambda^{2}, 2 \lambda^{2}$ -disilene $\left(\mathrm{Si}_{2}\right)$ is diamagnetic while disulfur $\left(\mathrm{S}_{2}\right)$ is paramagnetic $(\mathrm{S}=1)$. Draw ...
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D-orbitals of point group C2v

I'm trying to construct an MO diagram for cisplatin, which has C2v symmetry. However, there is no Mulliken label for the d(x^2-y^2) orbital in the character table. Does this orbital not form molecular ...
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Can atomic orbitals combine in a manner intermediate between bonding and antibonding?

When atomic orbitals combine in phase (0°) we get bonding molecular orbitals, and when they combine with opposite phases (180°) we get antibonding molecular orbitals. Why can't atomic orbitals combine ...
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Why does dilithium have a longer bond length than dihydrogen?

I've tried MO theory however they both have a bond order of 1. Which means we can not relate the bond order to the bond length. My thinking - I think that the h2 bond length is shorter due to only ...
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TD-DFT transition dipole moment vector does not align with experimental data

I have been modelling excited states of some molecules with similar stucture using TD-DFT theory, however, I have encountered an issue that sometimes transition dipole moment does not align with the ...
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What does Molecular Orbital Theory allow you to predict?

Molecular Orbital theory reveals the outcome when two atomic orbitals overlap. Almost all of the time we draw a Y axis with the notation of energy that can be described using electron volt units (eV). ...
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1answer
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Why are steric effects repulsive?

Normally, I think about orbitals interacting in the context of bonding. When two atomic orbitals overlap, they can do so in-phase or out-of-phase. The in-phase overlap results in a bonding molecular ...
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Interpreting data on molecular orbitals in GaussView 6.0 [duplicate]

Introduction I have been trying to use computational software to gain more insight into how molecular orbitals are formed, as well as their shapes and sizes in accordance with Molecular Orbital Theory....
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Diatomic molecule under pressure

If we put a diatomic molecule under pressure the interatomic distance will be decreased and according to this graph the potential energy of the bonding molecular orbital will be increased. What will ...
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Confusion regarding orbital, electron and Quantum no’s [closed]

Now , In some textbook I have read that orbital is nothing but the shape of electron . s,p,d orbitals etc. So , after knowing shape of an orbital . I got to know that inside the orbital is an electron ...
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What are “Secondary Orbital Interactions” in Organic Chemistry? [closed]

We used these to analyze the stability of molecules in an Organic Chemistry Course. My teacher analyses the stability of compounds on 3 levels: Atom level by studying the hybridization of the main ...
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1answer
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Comparing O−O bond length in hydrogen peroxide and dioxide(2−) ion

Problem How can we qualitatively compare the bond lengths between $\ce{H2O2}$ and $\ce{O2^2-}?$ Answer Attempt I tried using molecular orbital theory, but since both have peroxide $\ce{O2^2-},$ the ...
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Why electrons do not distribute evenly among the atoms in a molecule? [closed]

I was wondering why the state where electrons are evenly (or the closest to being evenly) distributed among the atoms in a molecule is not the lowest energy state? For example, in a water molecule it ...
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Rigorous but terse introduction to molecular orbital theory

Is there a terse but rigorous introduction to molecular orbital theory (MOT)? I'm looking for the 'Rudin's Real Analysis' of MOT, if that analogy resonates with anyone. If not, I'm looking for a book ...
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Why is oxygen more stable than oxygen dication?

According to molecular orbital theory (MOT), $\ce{O2^2+}$ has a greater bond order than $\ce{O2}$ and two less antibonding electrons. So why is molecular oxygen $\ce{O2}$ more stable than the ...
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Angle made by orbital with y-axis

What is the hybridization and angle (in degrees) with respect to the y-axis for the following hybrid orbital $ψ=\frac{1}{√3}c×(s-\frac{1}{√3}×p_x+\frac{√3}{√2}×p_y)$ The answer given is 30 degrees but ...
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1answer
265 views

Nature of a1g Molecular Orbital Interactions in Ferrocene

While learning about ferrocene I've come across this molecular orbital diagram. What particularly confused me is the nature of the a'1g orbital. My professor taught that a'1g and e2g are considered ...
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2answers
184 views

Explanation of the orbital energies resulting from Jahn-Teller distortion of octahedral complex using MO theory

I am confused about the energies of the orbitals after Jahn-Teller distortion of an octahedral complex. Take elongation for example. To my understanding, since the ligands on the $z$ axis move away, ...
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1answer
178 views

Frontier orbital analysis of zinc-catalysed carbonyl-ene reaction

Q1. Is the $\sigma_\ce{C-H}$ bond a donor in this reaction? If not, then can we take the alternate combination (HOMO of alkene, LUMO of the $\ce{C-H}$ bond and, HOMO of the carbonyl)? Q2. We can also ...
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82 views

Regarding the probability density of finding an electron in between a bond

I'd found the image attached on a website explaining the molecular orbital theory. My question is, shouldn't the graph have a maximum at the middle of the two hydrogen atoms? since my intuition tells ...
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are the exact and kohn-sham electron densities totally symmetric?

For any molecule with open or closed shells considering the electronic state to be the ground state: Is the exact electron density totally symmetric? is the Kohn-Sham electron density totally ...
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1answer
276 views

How can I know which molecule is more stable when bond order it's equal?

So, I was wondering, I have these molecules $\ce{O^+2}$, $\ce{O^-2}$, $\ce{O2}$ and $\ce{C^+2}$. When I try to find their bond order and their magnetic nature I get this: $\ce{O^+2} = \frac{1}{2} \...
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Can cycloaddition reactions be antarafacial?

Cycloaddition reactions of the form [4+2] and [2+2] are always suprafacial, as the geometry is too constrained to allow for antarafacial interaction between the FMO's. However, for cycloaddition of ...
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How do bonds rotate in pericyclic reactions?

In Pericyclic reactions, it is shown that the terminal bonds rotate (conrotation or disrotation) to allow for allignment of the FMO's, thereby forming the sigma bond However, a detail that most of my ...
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2answers
148 views

Half sigma bonds

$\ce{N2+}$ has $2$ $\pi$-bonds and a half sigma bond. First of all, how can a "half" sigma bond exist? Usually when we encounter non integral bond orders, it is mostly because of resonance ...

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