2
votes
1answer
20 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
62 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 ...
4
votes
1answer
78 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
52 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
53 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
40 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
86 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
91 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
78 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
181 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 ...
9
votes
1answer
164 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
75 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
92 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 ...
5
votes
1answer
128 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
175 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
56 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
124 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
26 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
143 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
41 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
225 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
62 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
147 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
83 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
375 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 ...
1
vote
2answers
99 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
114 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
39 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 ...
3
votes
1answer
44 views

Symmetry of an in-phase and an out-of-phase wavefunction “approaching” each other in an MO

Hiho. I have a question concerning this image (Chemistry, Catherine E. Housecroft et al., Pearson Education, 2010). In the text, it states the following: "Each of the new molecular ...
2
votes
1answer
65 views

Solution containing Iodine

The question is:- Iodine dissolves in a variety of solvents forming solutions that are purple, brown or any intermediate shade. This property is due to:- Hydrolysis of iodine ...
2
votes
2answers
123 views

Symmetry element in the coversion of cyclopent-2-enyl anion to pentadienyl anion?

I'm trying to draw the state correlation diagram for the reaction of cyclopent-2-enyl anion to pentadienyl anion but I don't know which symmetry element is preserved in this reaction. What could it ...
2
votes
2answers
125 views

Where does the 9th electron go in a $\ce{N=O}$ bond?

In the first resonating structure you can see 5 unpaired electrons and 4 shared electrons on nitrogen, then isn't this a extended octet? If it is so, then in which orbital that 9th electron is ...
1
vote
1answer
85 views

Which d-orbitals split according to CFT?

According to CFT, the degenerate d-orbitals split into $eg$ and $t_2 g$ groups. Are these the outermost nd orbitals which are vacant(4-d in case of 4th period) or the penultimate filled (n-1)d ...
3
votes
1answer
119 views

Bonding and nodes with molecular orbitals

If there is more overlap of the same sign wave function, this apparently leads to less energy. However, I don't understand why. My professor said that there would be less nodes, and less nodes means ...
1
vote
2answers
311 views

How does electron localization/delocalization work?

I can't find a simplified explanation on this topic. My textbook just adds to the confusion and all I'm really left with are more questions rather than answers. And adding to that question, does ...
1
vote
1answer
337 views

How can the Bonding in IF7 be explained using LCAO method?

I know that the VSEPR theory explains $IF_7$ (iodine heptafluoride)'s structure as a pentagonal bipyramidal one.The valence bond theory can be used to say that it has $sp^3d^3$ hybridisation(i think ...
1
vote
1answer
178 views

Molecular Orbital Diagram question

The molecular orbital diagram for $\ce{O2}$ says that the sigma 2p bonding molecular orbital is lower in energy than the pi 2p bonding molecular orbital. Why is this not the case in the $\ce{B2}$ MO ...
5
votes
3answers
308 views

LCAO (Linear Combination of Atomic Orbitals) and Phases

So when combining atomic orbitals to form molecular orbitals, you can either add the wave functions or subtract them. But at the same time, orbitals can exist in opposite phases (say one lobe of the p ...
9
votes
2answers
220 views

What utility does the Tau bond model of orbital overlap have?

In his book on molecular orbital theory, Molecular Orbitals and Organic Chemical Reactions, Ian Fleming notes that Pauling formulated an early alternative model to Huckel theory for explaining the ...
3
votes
2answers
443 views

Predicting molecular geometry from a formula

Can someone explain the following types of molecules and predict their structure and shape? It will help my understanding if you could provide an example. ...
5
votes
1answer
762 views

Resonance structure and hybridisation

I was given the first structure, and then drew the other 5 resonance structures. First of all, are they correct? ChemBioDraw had some complaints, but as far as I can see there's the same amount of ...
3
votes
1answer
260 views

Energies of atomic orbitals on molecular orbital diagrams

When we plot molecular orbital diagrams we use a linear combination of atomic orbitals. Where can I find the energies of particular atomic orbitals? In the picture below, the energies of 2s and 2p ...
2
votes
2answers
101 views

How does expansion of electron shells work?

How does it work? I've read that its about the similarity of the energy levels of $3d$ and $3p$, but shouldn't the electron shell $4s$ be filled before $3d$ if filled? So what is done with the $3d$? ...
6
votes
2answers
408 views

Bonding and anti-bonding orbitals in the light of time-dependent Schrödinger equation?

In organic chemistry, people draw 2p orbitals like this: and then they explain how the orbitals combine to non-bonding (π*) or bonding (π) molecular orbitals, like this: depending on whether the ...
4
votes
2answers
412 views

Why are these molecular orbitals invalid for hexatriene?

Here are the MOs (more accurately, the breakdown of the MOs) for conjugated hexatriene: Now, when first asked to draw the MOs myself, I drew this one for $\psi_3$: It still has two nodes, and is ...
7
votes
5answers
1k views

Carbon with 5 bonds?

I've heard that, even though according to Molecular Orbital Theory there is no chance of having nobel gases bonded to each other, it is not totally impossible. For example, under extreme conditions, ...
4
votes
1answer
260 views

Help understanding localized bonding theory

So I understand molecular orbitals and how to do VSEPR models, but I seem to be struggling with understanding localized bonding theory and how to do hybridizations. After drawing the initial lewis ...
7
votes
1answer
197 views

Molecular and Atomic Orbitals and Antibonding

When two atomic orbitals make one molecular orbital there must be an antibonding orbital also. Why should they make also an antibonding molecular orbital.
9
votes
5answers
2k views

What is the chemical structure of H₂SO₄?

I was looking at the chemical structure of H2SO4. Intuitively, I would have expected this molecule to be square planar in a p2d2 or sp2d geometry but rather, it is shown to be in an tetrahedral ...
8
votes
4answers
216 views

Hierarchy of electronic wavefunctions

The previous question contained too much unnecessary information and was edited. I am wondering about the "hierarchy" of wavefunctions. If one can combine atomic orbitals (AO) into molecular orbitals ...