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.

Filter by
Sorted by
Tagged with
5
votes
1answer
2k views

Why does [Co(NO2)6]4- ion have 3 unpaired electron as opposed to 1?

Why does $\ce{[Co(NO2)6]^4-}$ ion have 3 unpaired electron as opposed to 1? The book says that it has 3 unpaired electrons. I thought $\ce{NO2-}$ was a strong field ligand, making $\ce{Co^2+}$ a $\ce{...
-1
votes
0answers
29 views

Valence Bond Theory and double sigma bonds

I naively use Valence Bond Theory to analyze dicarbon. Both carbons spontaneously excitate from 2s2 2p2 to 2s1 2p3. Both 2s orbitals overlap head-on to form a sigma bond. Both 2pz orbitals overlap ...
2
votes
1answer
269 views

Electron pairing in atoms

A question asks: This question refers to isolated gaseous atoms. In which atom are all electrons paired? Ba, Br, S or Si? I thought it was Ba as its electron configuration is [Xe] 6s2. However, ...
3
votes
0answers
34 views

Why does the binding of DMSO to metal via the S atom (k-S) strengthens the S=O bond?

So, DMSO (dimethyl sulfoxide) can form metal complexes in both $\mathrm{\kappa O}$ and $\mathrm{\kappa S}$ mode i.e. binding with the oxygen or the sulfur respectively. The general explanation given ...
-1
votes
0answers
40 views

Hybridized orbitals and molecular orbital theory

When hybridization was introduced in the late 30's to explain the structure of methane , first it was considered that bonds between valence electrons of carbon in different atomic orbitals will have ...
7
votes
2answers
464 views
0
votes
0answers
11 views

MO analysis of a radical reaction of chlorine radical with methyl radical

Im trying to create an MO energy diagram for the reaction of a chlorine radical with a methyl radical by creating the 5 group orbitals for methyl radical(with pyramidal geometry) and then creating ...
1
vote
0answers
29 views

Does the number of bonding MOs always equal the number of antibonding MOs

In (I think all) of the molecular orbitals (MO) diagrams I have seen, I have observed that the number of antibonding molecules is the same as the number of bonding molecular orbitals. Here are some ...
0
votes
1answer
60 views

Why is the HOMO-LUMO gap in N2 and CO of different sizes? [closed]

Why is the HOMO-LUMO gap in $\ce{N2}$ and $\ce{CO}$ different even though they have the same number of valence electrons?
2
votes
2answers
11k views

Where does the 9th electron go in a 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 ...
0
votes
0answers
32 views

How many π-electrons are there in 2-methylene-2H-pyran?

I thought that the structure will be aromatic and stabilised because one of the lone pairs being delocalised with the help of conjugated double bond system but still only 3 π-bonds will be present at ...
2
votes
1answer
160 views

Geometry of Ni(acac)2

The complex $\ce{Ni(acac)2}$ is paramagnetic as expected , i.e it has two unpaired electrons giving rise to a magnetic moment of $ \sqrt{8}$ BM but doesn't have the tetrahedral geometry consistent ...
4
votes
2answers
837 views

Which atom bears the negative charge in cyanide? I am confused by the MO diagram

In heteronuclear species, whichever atomic orbital a molecular orbital is closer to in energy contributes more to that molecular orbital, right? In other words, if the orbital is occupied, more ...
18
votes
2answers
65k views

What are t2g and eg in CFT?

In the crystal field theory (CFT), when the splitting of the d-orbital occurs, it gets divided into two parts. The upper part with higher energy is the $\mathrm{t_{2g}}$ and the lower part with lower ...
4
votes
1answer
59 views

How to understand the (non-)degeneracy of states of singlet Σ and Δ terms for a ππ configuration of two nonequivalent electrons?

As instructed in Levine's Quantum Chemistry 7th edition, Chapter 13.8, page 377, for a $\pi \pi$ configuration of two nonequivalent electrons, four functions $\pi_{+1}(1) \pi_{-1}^{\prime}(2)$, $\pi_{+...
1
vote
1answer
18 views

Mathematical equivalence of ionic-bond resonance structures and d-orbital participation in hypervalent molecules

It is now routine in the scientific community that "main-group hypervalent molecules, under certain conditions, tend to be better represented by resonance structures involving ionic bonds, rather than ...
3
votes
1answer
65 views

How to perform Mulliken population analysis by hand with GAMESS output?

I did a simple calculation on hydrogen fluoride with GAMESS and I wanted to reproduce the Mulliken population analysis for atomic orbitals. A molecular orbital is a linear combination of atomic ...
1
vote
0answers
20 views

pi-type bonding interaction along the bond

I was given the diagram of $\ce{BF3}$'s LUMO and asked to assess its bonding character as shown below: Below is the model answer for the annotated version. I managed to correctly answer the HOMO MO ...
0
votes
0answers
98 views

Molecular orbital diagram of hydroxide ion?

I would like to understand how to create a molecular orbital diagram for the hydroxide ion from scratch. This includes understanding the shape of the molecular orbital. Here is an attempt I have come ...
3
votes
1answer
46 views

Symmetry of an FO

I want to ask a question about the symmetry of an FO for $\ce{[CuL2]^-}$ where L is a $1e^-$ donor sigma bonding ligand (e.g. Me). For the ligand orbitals, I produced the following orbitals shown ...
0
votes
0answers
19 views

Books for organic chemistry [duplicate]

What is the best book to start organic chemistry once I know the basic knowledge of reaction mechanisms like substitutions (nucleophilic, electrophilic and some basic other mechanisms that are given ...
0
votes
2answers
78 views

Questions in MO theory

Τhe electrons in the antibonding MO are the unpaired electrons of the molecule? E.g. $\ce{O2}$, by writing down the diagram for the MO we notice that there are only 2 electrons in the top antibonding ...
2
votes
2answers
26k 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 ...
2
votes
1answer
78 views

Effective Bohr Radius in Transition Metal Complexes?

I am playing around with a toy model of a transition metal complex where the HOMO are $d$-electron states of predominantly transition metal character. Let's say this is a $d^1$ (or $d^9$) system and ...
9
votes
1answer
120 views

Hybrid orbitals, photoionization and time dependence

Wikipedia, in the article on Orbital Hybridisation, states the following: One misconception concerning orbital hybridisation is that it incorrectly predicts the ultraviolet photoelectron spectra of ...
72
votes
4answers
31k views

Bonding in diatomic C2, a carbon-carbon quadruple bond?

Carbon is well known to form single, double, and triple $\ce{C-C}$ bonds in compounds. There is a recent report (2012) that carbon forms a quadruple bond in diatomic carbon, $\ce{C2}$. The excerpt ...
0
votes
0answers
21 views

Energy Levels of Molecular Orbitals formed by combination of Atomic Orbitals

In general when we talk about chemical bonding, we say that it is "nature's way to stabilize the systems" and the energy of the molecule formed by atoms will be lower than that of the individual atoms;...
1
vote
0answers
9 views

Energy diagram of copper iodide complex

We did an experiment where copper iodide 4-methylpyridine and copper iodide imidazole was formed and now we are asked what orbital the electron is excited from and to. After much research we still ...
-1
votes
1answer
41 views

Question about d-orbitals [closed]

I saw somewhere that, "in PF5, the 3d orbitals of phosphorus end up in the anti-bonding molecular orbitals, and thus contribute less to the final molecule" and that "the hypervalency of some ...
4
votes
1answer
305 views

Question about the role of d-orbitals in polarisation

I know that, although many elementary books say that d-orbitals are involved in the bonding of hypervalent main group compounds period 3 or higher such as the sulfate ion but in reality they are only ...
3
votes
0answers
42 views

Overlap matrix for finite sized square lattice of hydrogen atoms

So I'm trying to use the LCAO method to calculate molecular orbitals on a square lattice of hydrogen atoms. To this end, I need to compute the Hamiltonian matrix. With the nearest neighbor interaction ...
3
votes
1answer
199 views

Formation of trifluoride anion

I wanted to understand mechanism of the formation of $\ce{F3-}$ anion through the molecular orbital theory. UPDATE - What I really want to know is that when $\ce{F3-}$ is formed from $\ce{F2-}$ and $\...
0
votes
1answer
58 views

Why must there be degeneracy in the orbitals to have a Jahn-Teller effect? [closed]

Why is it the case that for Jahn-Teller effects to occur in transition metals there must be degeneracy in either the $\mathrm{t_{2g}}$ or $\mathrm{e_g}$ orbitals?
5
votes
0answers
146 views

diborane fragment orbitals energy of dihydrogen

I want to ask a question about the fragment orbitals of the $\ce{B2H6}$ system, specifically when I combine the $\ce{B2H4}$ with the $\ce{H2}$ fragments. I am halfway through my inorganic chemistry ...
0
votes
0answers
29 views

Sigma bond by combining two p orbitals

If I combine two p orbitals in such a way that they form σ bonds, which linear combination will represent bonding and antibonding? My work on this problem: $$ \begin{align} &\text{Bonding:} &...
3
votes
0answers
23 views

Energy level of molecular orbitals in heteronuclear diatomic compounds

I have been studying the molecular orbital theorem. I read that the energy levels for the $\ce{p}$ orbitals in the first series of $\ce{p}$ block molecules are something to the tune of $$\pi_x=\pi_y&...
7
votes
1answer
160 views

Energies of Virtual Molecular Orbitals (LUMO)

I just had a question about molecular orbitals. I was just wondering if the energies of the LUMO (virtual orbitals) derived from CCSD(T)/cc-pTVZ calculations could be trusted. I remember reading some ...
13
votes
3answers
4k 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 ...
7
votes
0answers
200 views

Mathematical relation between bond angle and fraction of s or p character

In Concise Inorganic Chemistry by J.D.Lee (Adapted by Sudarsan Guha, Fourth Edition), on page 75, under the topic "Effect of Electronegativity - When the surrounding atom is same with different ...
18
votes
4answers
1k views

Does a neutral dimercury molecule exist?

Is a neutral $\ce{Hg2}$ molecule possible, as a gas under extremely low (partial) pressures? What is the enthalpy of formation or similar? It is my impression that usual mercury vapors are monatomic? ...
2
votes
1answer
69 views

Is there a hypervalent molecule which has no contribution of d-orbitals at all?

I thought that d-orbitals were used to "extend the octet rule" in these molecules until I looked it up on Google and saw that they actually contributed only a little to the molecule. A little, but not ...
2
votes
1answer
75 views

Relative Energies between LGOs and 2s orbital of oxygen in H2O MO Diagram

In this MO diagram, we find that the LGOs of the two premixed H1s orbitals are significantly higher in energy than oxygen's 2s orbital. Although oxygen's $Z_{eff}$ is considerably higher, is it really ...
4
votes
1answer
95 views

On mathematics behind molecular orbital energies

When explaining the mathematics behind calculating molecular orbital energy , namely HOMO and LUMO energies, using quantum chemistry, Chainer Chemistry documentation states that From mathematical ...
1
vote
0answers
31 views

Stabilizing donor-acceptor interaction between orthogonal orbitals in the SN2 transition state?

For the $\mathrm{S_N2}$ reaction between chloroacetone and iodide, my professor has drawn a donor-acceptor interaction between the iodine lone pair attacking the Cl-substituted carbon and the π ...
2
votes
0answers
33 views

Varying sizes in LUMO of acrolein

I want to ask a question about the varying sizes in the LUMO of acrolein during a 1,2- or 1,4-addition. Today in our introductory lesson to Organic Synthesis with 1,2- and 1,4-addition we were ...
-2
votes
1answer
135 views

Sulfur can violate the octet rule because it has an “empty D orbital” is there any other information the periodic table isnt telling us?

In sulfur or any atom with an expanded octet on the 3rd row, where does the idea that they have an empty D orbital come from ?
2
votes
0answers
21 views

How to deal with non-symmorphic space groups for orbital/vibrational analysis?

I am learning about how to apply group theory analysis of MO diagrams and vibrational in the solid state context (not isolated molecules). I think the strategy for calculating representations and ...
1
vote
0answers
43 views

Calculating the Molecular Orbitals of a Molecular State [closed]

I am performing ab initio calculations on a heteronuclear diatomic compound using the MRCI method on the MOLPRO quantum chemistry package. I obtained the molecular states of the compound but I was ...
1
vote
0answers
207 views

What is the purpose of phase matching when drawing a MO diagram?

During the lecture, we were learning how to draw the MO diagram for $\mathrm{BF_3}$. I understand that only orbitals with the same symmetry labels can interact and form molecular orbitals. My ...
2
votes
0answers
27 views

Properties that probe electron kinetic energy

This post is inspired by a question regarding the meaning of off-diagonal elements of the KE matrix (in some AO basis). One answer suggests that a diagonalized KE matrix might not be very useful. I ...

1 2 3 4 5 12