0
votes
0answers
8 views

What are the molecular orbitals of the hypothetical linear H₃⁺ molecule?

What would be the wave function of the lowest energy molecular orbital of a hypothetical linear H3+ molecule? According to the LCAO method, I feel the lowest energy MO will be 1s(A) + 1s(B) + 1s(C). ...
1
vote
1answer
17 views

Delocalization of pi electrons in nitrate ion

In my textbook, as examples of delocalization of pi electrons, benzene and nitrate ion have been considered. Benzene, due to symmetry of its resonating structures is simple enough. We assume that ...
2
votes
1answer
37 views

How to explain the effect of hyperconjugation on the stability of alkenes with MO theory?

Hyperconjugation stabilizes carbocations and that makes sense because electrons are given to the empty p orbital. But how does it stabilize alkenes ? Can MOT be used to explain it ?
3
votes
1answer
26 views

Non stationary effects of molecular orbitals

We have been learning a bit about molecular orbitals in class. However, we have always considered things under a quasistatic approximation. What are some effects that can only be explained by not ...
1
vote
1answer
34 views

How is ethanenitrile protonated?

I know that the proton will attack the HOMO, but I'm having difficulty imagining how this will happen. Thank you.
3
votes
1answer
94 views

How can BN be paramagnetic?

I read something recently that said "BN has been observed in the gas phase, is paramagnetic, and has a vibrational frequency lower than N2. These properties can be explained by the molecular orbital ...
2
votes
1answer
169 views

Why does AlCl3 dimerise to Al2Cl6 at low temperatures?

I know that it has something to do with HOMOs and LUMOs (I can't what the HOMO/LUMO for AlCl3 is, though).
0
votes
0answers
23 views

Relating Molecular Orbital Theory and Valence Bond Theory

As I have studied both the theories only superficially, I am unable to correlate them. I would like to know the link between the two.
0
votes
1answer
34 views

Molecular Orbital Theory and No. of bonds

The order of filling of molecular orbitals $\ce{O2}$ by MOT is this : But from it, how can I deduce that there is one sigma and one pi bond in an oxygen molecule ?
2
votes
1answer
152 views

The “rules” for LCAOs in Molecular Orbital Theory

In our course on physical chemistry, which involves MOT, we have been taught that in the LCAO approach, the wave function for a molecule... say hydrogen ion, can be approximated by a linear ...
2
votes
2answers
91 views

Why is an excited helium dimer created in this collision experiment?

Why does a collision between an excited helium molecule (He*) and a ground-state helium atom create He2*? Is it something to do with the lower-energy orbitals? I'm not really sure at all.
2
votes
1answer
36 views

MO theory methods other than LCAO

What methods other than linear combination of atomic orbitals does MO theory use? Which one is the most accurate and comprehensive?
2
votes
1answer
89 views

Why hybridization occurs in diatomic molecule

In diatomic nitrogen There are two electron configurations I'd like to compare: 1s2 2s2(lone pair) 2p3(the bonding electrons sigma,pi,pi) 1s2 2sp(lone pair) 2sp(sigma bonding) 2p2(pi,pi bonding) ...
1
vote
1answer
105 views

C=O and C=C antibonding orbitals

Why is the pi star orbital of the C=C bond higher in energy than the antibonding pi orbital of the C=O bond? I thought it was the other way around; it's relatively easy to add something to a C=C ...
3
votes
0answers
50 views

Irreducible Representations to Classify Atomic Orbitals [duplicate]

I have some major confusion on Irreducible Representations. An example of a problem i have is Based on the character table for the point group of each of the follwing molecules, which irreducible ...
5
votes
1answer
584 views

What are t2g and eg in CFT?

In the Crystal Field Theory, when the splitting of the d-orbital occurs, it gets divided into two parts... The upper part with higher Energy is the $t_{2g}$ and the lower part with lower Energy is ...
5
votes
1answer
112 views

Diatomic halogens - bond strength

Why is the F-F bond relatively weak? And why does bond strength decrease from Cl-Cl to I-I? Does this have anything to do with "lone-pair" repulsions on the rather small F-F molecule? I haven't ...
3
votes
1answer
36 views

Structure of benzene

How does molecular orbital or valence bond theory explain the delocalised structure of benzene? I.e. when the carbon forms 3 bonds with other carbons/hydrogen, what happens to the remaining hybridised ...
0
votes
1answer
108 views

How do you determine how many electrons occupy the anti bonding orbitals?

For molecular orbital theory: How do you determine how many electrons occupy the anti bonding orbitals? Also, why does hydrogen gas have no anti bonding orbitals- if each atom's electrons form a ...
4
votes
1answer
89 views

Asymmetry in trigonal bipyramidal geometry

I teach an MCAT course in chemistry. I like to explain VSEPR by saying.. first, imagine arranging electron pairs around the central atom so they are maximally distant from each other, and uniformly ...
5
votes
1answer
170 views

Show the vibrational frequency of F2- is much lower than that of F2

Basically I need to draw the molecular orbital for $\ce{F2}$ and then answer a bunch of questions about it. I have drawn it correctly, as far as I know, but I don't know how to use it to show that the ...
6
votes
2answers
399 views

How does a Frost diagram reproduce the solutions to the wave equation?

I came across a Frost diagram for cyclic compounds in my book, and all my book had to offer was that it geometrically reproduces the solutions of the wave equation, and can therefore determine the ...
2
votes
1answer
34 views

Quick way to find magnetic nature of compounds or ions

According to the Molecular Orbital Theory, the method to check whether a given compound is paramagnetic or diamagnetic is to draw the molecular orbitals and then to see whether we have all the ...
3
votes
1answer
85 views

Unequal ionization energies of methane

Why does methane have two different ionization potentials? How does this work? I understand that MO theory predicts C-H bonds of differing strength, while hybridization predicts C-H bonds of varying ...
5
votes
1answer
156 views

What is the point of introducing virtual orbitals in Hartree-Fock calculations?

Let us for simplicity discuss RHF formalism. For $2n$-electron system we have $n$ Hartree-Fock equations written for $n$ spatial orbitals $\{ \phi_{k} \}_{k=1}^{n}$ $$ ...
2
votes
1answer
165 views

Which one, Mulliken charge distribution and NBO, is more reliable?

Sometimes the Mulliken and NBO turn out to be so different that I can't decide which one I can trust. I've heard that Mulliken is inaccurate, but is NBO always accurate? And should I use Gaussian or ...
0
votes
1answer
137 views

Nitric Oxide Dimerization

This is the molecular orbital diagram for nitric oxide: Now, we know that nitric oxide can dimerize. However, why does nitric oxide dimerize as to form an $\ce{N-N}$ bond? Why not an $\ce{O-O}$ ...
2
votes
1answer
155 views

Position of nodal planes in molecular orbitals

From the attached picture (MO diagram of cyclopentadienyl anion) I can figure out where the nodal planes are, but why are they exactly at these positions? Why is this nodal plane invalid?
3
votes
1answer
313 views

Energetic Placement of Atomic Orbitals in the HCl Molecular Orbital Diagram

How are the 3p orbitals of chlorine lower in energy than the 1s orbital of hydrogen?
3
votes
2answers
861 views

Why are least electronegative elements usually in center of lewis structure

Many sources state that one of the primary rules for molecular structures is that the least electronegative element is in the center. However, none of them explain why this is the case. Is this ...
5
votes
1answer
102 views

Electronic model with highest prediction rate

Among many models, including the valence bond model (VB) or the molecular orbital (MO) model, which are the ones with best predictive power? (e.g. the MO is thought to predict spectroscopic ...
6
votes
3answers
315 views

Do filled Orbitals also hybridize?

Recently I was watching a video on Valence Bond Theory, on the MIT Open-Course youtube channel. The teacher there said that for hybridization to occur, electron promotion from fully filled orbitals to ...
13
votes
1answer
412 views

When is it true that more nodes equals higher energy?

Consider all the MOs of some isolated molecule. (It could be a single atom too; I'll use MO to refer to AOs as well.) Number them in increasing order of the number of nodes (node = surface where the ...
4
votes
1answer
123 views

Why Aren't Chlorides Of The Noble Gases As Prevalent As Their Fluorides?

I can't find the answer to this question on this SE website, and I apologize for the repetition if it has been answered before. It is my understanding that compound formation has only been observed ...
5
votes
2answers
145 views

Counting Nodal Planes in cyclopropane

The energy of molecule orbitals increases with more nodal planes. W1 (in the attached picture) has no nodal plane. I'd like to know how to draw the nodal planes in cyclopropane molecule orbitals but ...
6
votes
2answers
165 views

What is the origin of the differences between the MO schemes of O2 and N2?

Here are the MO schemes of $\ce{N2}$ (left) and $\ce{O2}$ (right). Why is the $\sigma$-MO formed by the $p$ AOs energetically above the $\pi$-MO for $\ce{N2}$ but not for $\ce{O2}$? Can it be ...
7
votes
3answers
791 views

Why is the bond angle H-P-H smaller than H-N-H?

$\ce{N}$ & $\ce{P}$ are along the same group. $\ce{NH3}$ and $\ce{PH3}$ have one lone pair and both the central atoms are $\ce{sp^3}$ hybridized. But inspite of that, the former's bond angle is ...
1
vote
1answer
76 views

Molecular orbitals and “generalized” aufbau principle for heteronuclear molecular configurations

Is there any general ordering or rule for heteronuclear molecules like $\ce{AX_2}$, $\ce{AX_{n}}$, and their molecular bonding/antibonding configurations ($\sigma/\pi$ orbitals) accordingly to some ...
1
vote
2answers
311 views

Difference between backbonding and hyperconjugation and conjugation [closed]

What is the difference between backbonding and hyperconjugation and conjugation? I mean the basic differences as all are concerned with donation of electrons. What is the most striking effect of each ...
0
votes
0answers
46 views

Argon chemistry, molecular geometry and hybridisation

Can Argon hybridize orbitals and/or form covalent-like/ionic-like compounds? Is there any study of that?I would be happy to read concrete references... What kind of molecular geometries for argon ...
3
votes
3answers
325 views

PI Bonding in Carbon Dioxide

I am fairly sure the first diagram I drew for carbon dioxide is wrong in terms of showing pi bonding. This is because we use a pi orbital twice, which isn't possible. The second diagram corrects this ...
3
votes
1answer
47 views

Fourth principle of Molecular Orbitals

The fourth principle of Molecular Orbitals state that: Molecular orbitals are best formed when composed of Atomic orbitals of like energies. I'm not sure about ...
3
votes
2answers
302 views

Why does cyclopropane give bromine water test?

This question was in my exam and all I could tell was that it is related to high angle strain as the angle is $60^\circ$ in stead of required $109.5^\circ$. No book I have read mentions this. Also, ...
2
votes
2answers
70 views

Can a s orbital overlap with any p orbital to form a sigma bond?

In internet resources, only $p_z$ orbitals are shown to overlap with $s$ orbitals to form sigma bond. But my teacher says that according to Valence Bond Theory, $s$ orbital overlaps with all three ...
9
votes
1answer
167 views

Hyperlithiated Carbon Species

Below is replicated Question 1 from the Final Qualifying Exam of the Australian Chemistry Olympiad, 2004B, here. Question: The theory of promotion-hybridization is quite successful at explaining why ...
2
votes
1answer
106 views

Why is the 8-electron rule more important than the 2- or 18-electron rule

Why is the fulfilled electronic configuration of only $p$ orbital is stable. I mean why $II-B $ group with fulfilled $d$ orbital,$II-A$ group with fulfilled $s$ orbital...are not stable. Why makes ...
10
votes
4answers
2k views

Bond Length of CO+ is expected to be more than CO but it is found to be less. Why is this so?

According to Molecular Orbital Theory(MOT), the bond order of CO is 3. When CO+ is formed, bond order decreases to 2.5 and thus bond length should increase. However, the bond length of CO+ is found to ...
2
votes
2answers
205 views

Structure of NO2 compound?

What is the correct structure for the NO2 compound (not ion)? I always thought it was like: since the negative charge would be residing the on the highly electronegative oxygen, but was reading ...
2
votes
2answers
219 views

A molecule absorbs light having a specific wavelength, why doesn't it absorb shorter wavelengths?

I am currently studying computational chemistry and I am trying to understand the UV-VIS absorption of molecules. I know that UV-VIS absorption is electronic excitation and requires a specific energy. ...
0
votes
0answers
89 views

Constructing a MH6 MO diagram

I'm wondering how I'd construct an MO diagram for a MH6 complex, M is transition metal and the complex is a linear edge-sharing octahedra chain. This is with a view to potentially constructing a band ...