Questions tagged [symmetry]
The description of the symmetry present in molecules. Molecular symmetry is useful for explaining or predicting of a molecule's chemical properties.
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Molecular orbital energies for CH4 using group theory
I was learning how to use symmetry in molecular orbitals, I started with $\ce{CH4}$ the point group is $T_d$ I get the reducible representation for methane the reduce it to be $T_2+A_1$, the I applied ...
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Electronic configuration and symmetry labels of 3d$^7$ ions
In 3d$^7$ ions, e.g. Co$^{2+}$, the ground state is $^4$F, and it contains different levels due to the crystal field, such as $^4T_{1g}$, $^4T_{2g}$ and $^4A_{2g}$. Can anyone tell me what exactly ...
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How do two orbitals need the same symmetry to bond? Do they need the same mulliken label?
I heard that in order for two atomic orbitals to form a bonding molecular orbital, they need:
Similar energy
Similar symmetry
and Possibility of overlap with the same sign
but, for example in methane, ...
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Why can s and p orbitals of one atom form hybrid orbitals but the overlaping of s & p orbitals of two different atoms don't form a molecular orbital?
So my question is in the title : Why can s and p orbitals of one atom form hybrid orbitals but the overlapping of one s orbital and one p orbital (perpendicular to the bond axis) of two different ...
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H-NMR Analysis of C15H24O
I was able to figure out that the structure of this compound was a benzene ring with 2 equivalent trimethyl groups to give the 18H singlet. Another non-equivalent methyl group to give the 3H singlet. ...
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How do you determine point groups of more complex molecules when there are 2 or more central atoms?
I am trying to determine the point group of Fe2(CO)8 and am having difficulty with the bond angles and geometry. How would one go about this in a logical sense?
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Bromate ion point group?
Would the bromate ion have C3v point group due to the trigonal pyramidal geometry? I see a C3 rotational axis and a vertical plane of symmetry. Am I missing anything in terms of the double bonds or ...
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What prevents an octahedral complex from always assuming the quadratic planar limiting case, due to the Jahn–Teller distortion?
When a given high-spin complex is Jahn–Teller distorted, this does not change the relative position of the total energy of the complex (assuming $\mathrm{d^{10}}$ configuration).
Indeed, the ...
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What does the 2 in t2g stand for?
I have read so far that it is about whether the d-Orbital is symmetric to a C2 element perpendicular to its main rotational axis. If all the given orbitals in a group are symmetric to that element, ...
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Why is prismane explosive but cubane is not?
So I was reading about polyhedral hydrocarbons, because I dig the topic, and I read (admittedly on wikipedia entries... But they cited papers, I swear!) that prismane is explosive due to the massive ...
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How does the anti isomer below have a plane of symmetry? The R group and the H end up in opposite sides if you divide in half [closed]
If we add substituents R to this structure, we can have two diastereoisomers with the two R groups on the same side (syn) of the flat ring or on opposite (anti) sides. Although the plane of the paper ...
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Energy of d(x²-y²) and d(xy) orbitals the same with respect to trigonal symmetry?
In the orbital splitting diagrams of trigonal planar and trigonal bipyramidal complexes the d$_{x² - y²}$ and d$_{xy}$ orbitals have the same energy. I have always assumed that this is because they ...
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Deduce the shapes of stretching modes of a tetrahedral molecule
This question is in relation to the [FeCl4]- molecule, which is tetrahedral. I previously deduced, using symmetry analysis, that the vectors corresponding to the bonds of the molecule will be A1+T2, ...
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What's the relation between two symmetry groups, if one has all the symmetry of the other and some more?
Question:
Consider two molecular symmetry groups, for example $C_s$ and $C_{2v}$.
$C_s$ has one inversion plane, and two irreductible representations: the symmetric $A'$, and the antisymmetric $A''$.
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Why are certain lattices compatible with only certain point groups and not all point groups?
I will limit this discussion to 2 dimensions for ease of intuition. My understanding of the 17 crystallographic plane groups is that these 17 groups represent all the possible symmetry groups of any ...
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How do I assign functions for cartesian coordinates and rotations to irreducible representations of a character table?
I do not really understand the intuition behind the functions assigned to irreducible representations.
For example, in H₂O, the A₂ representation is given by
...
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Is there a difference between $A_{1g}$ modes and $A_{g}$ modes?
I know that both are totally symmetric and that the '$1$', according to the Mulliken table, refers to symmetry around the $C_2$ axis but I was reading some papers and found that modes were sometimes ...
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Are A1g modes reduced at 180 degrees polarisation in Raman spectra?
I have read that A1g modes are identifiable in Raman spectra by looking at cross-polarised Raman spectra and seeing peaks that strongly reduce in intensity. So essentially, the intensity of A1g modes ...
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Point group of harmonic oscillator
The book Molecular Quantum Mechanics by Atkins and Friedman [1] says the point group of a harmonic oscillator is $C_\mathrm{s},$ composed by the identity operator $E$ and a reflection $\sigma_\mathrm{...
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Factor Group Analysis of Na2SO4 - Site Group Symmetry
I'm still trying to understand how to construct a factor group analysis for a given molecular point group and the resulting solid state group symmetry. For this I searched for some examples and found ...
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Relation between symmetry of a reciprocal vector and lattice planes perpendicular to it
What is the relation the symmetry of a high-symmetry point in the first Brillouin zone and lattice planes perpendicular to it? Are the two symmetries equivalent?
I have this question because I want to ...
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What does it mean that a state belongin to a given irrep transforms like $Rx$, $Ry$ or $Rz$
The present question is related to this other question I did few days ago.
Given a point group and the list of the irreps (see for example here) the meaning of an irrep which transforms like $x$ or $x^...
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When does the angle between the planes in tetrahedral molecule with central atom deviate from 90°?
Consider an atom X bonded to four other atoms A, B, C, D in a tetrahedral fashion with sp³ hybridisation. If A, B, C, D are the same, every bond angle is 109.47°, and the angle between the planes ...
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How do I show that a transition is electric dipole allowed with group theory/symmetry?
This is actually a follow up of this question
The follow-up is not because of the electric instead of magnetic dipole (this is trivial).
It is because I'm interested in extra info.
Suppose I have a ...
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What is m.2m point group?
I'm using Bilbao Crystallographic Server to find 3D crystallographic point groups of the K points of anatase TiO2.
Since the space group of anatse TiO2 is $I4_1/amd$, on this page, I found the point ...
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Determination of energies in MO diagrams
How do we determine the relative placements of molecular orbitals in their diagrams? I understand that we can use point groups to find symmetry-allowed interactions between orbitals that we write on ...
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is this compound meso? trans-1,4 dimethylcyclohexane [duplicate]
I had a question on a quiz that asked if the compound below was meso or not. I thought that it would be meso because there is a plane of symmetry going through the two methyls, but the answer was that ...
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How do we find the SALCs?
I am trying to understand exactly what IRREPs are and, in order to know more about it, I started reading the chem.libretext course on molecular symmetry which up to this point seemed fairly ...
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What does it mean by non-bonding p pi orbital?
In a paper by Peng et. al.,[1] I read about the valence band maximum of $\ce{TiO2}$ consists of non-bonding O pπ orbitals
... the valence band maximum (VBM) consists of non-bonding O pπ states
What ...
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Why are there only 14 types of Bravais lattices and not 28 when there are 7 types of unit cells and each can have four variations?
As the title suggests, I can't understand why certain kinds of variations (like Face-centred or Body-centred) are restricted to certain types of unit cells. An orthorhombic unit cell has Primitive, ...
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Of 2-bromobutan-2-ol and trans-1,2-dimethylcyclobutane which is chiral as well as dissymmetric?
In an examination I was asked to determine the molecules which are chiral as well as dissymmetric. There were four options, and among them, two were achiral, as they had an improper axis of symmetry. ...
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Why does twistronic 'magic angle' graphene have only 180-degree symmetry?
From Graphene superconductors may be less exotic than physicists hoped[1]:
Excitement rose earlier this year with the discovery of
superconductivity in a similar
system[2]:
three layers of graphene ...
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Why does an improper rotation axis preclude chirality?
Can anybody prove that any molecule with an axis of improper rotation is nonchiral? I still do not understand why this is so, any proper mathematical proof or visualisation of a generalised molecule ...
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d orbital irreducible representations in metal in ML4 model [closed]
In ML4 (Metal—4 ligands)model which has a square planar shape and D4h point group, what is the irreducible representation for the 5 kinds of d orbitals in the central metal?
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Using symmetry and group theory arguments to explain iron(II) in a tetrahedral crystal field
I am trying to figure out how to explain $1s \rightarrow 3d$ spectroscopic transitions for $\ce{Fe^{2+}}$ in $T_\mathrm{d}$ symmetry. These transitions make up the pre-edge region in K edge X-ray ...
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High symmetry points and x-coordinates
Is it possible to work out the x-coordinates related to high symmetry points?
The software I'm using doesn't provide me with that, so I was wondering if there is a way to manually figure it out, as I ...
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How many stereoisomers are present in octahedral complexes of type MA3B2C?
Does $\ce{MA3B2C}$ type have optical isomerism or just geometric isomerism? I was told that it has three isomers, two cis and one trans. Are the two cis isomers optically active?
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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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Why does hydrogenation of this compound not result in a diastereomeric mixture? [duplicate]
In a question, this compound was given and it was asked:
"Hydrogenation of the above compound in the presence of poisoned Palladium catalyst gives?"
When I was answering it, I thought that ...
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Why is the base-centered orthorhombic crystal lattice a unique crystal system?
I'm having difficulty understanding why the base-centered orthorhombic crystal system is a unique crystal system. When I draw two base-centered orthorhombic unit cells next to each other there appears ...
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Planes of symmetry of a molecule
Are we limited to use only xy, yz and zx planes to check for planes of symmetry of a molecule? Because I see a plane of symmetry in the following molecule through the two shown H atoms or OH groups. ...
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electronic transition for polyenic molecules
I am having troubles with polyenes states symmetry.
I found an exercise on the pentadien, where they ask us to analyze the symmetry of the singlet excited states corresponding to:
State S1: π+ →π+
...
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How are there two C3 rotation axes in ammonia?
If we look at the character table for the $C_\mathrm{3v}$ point group (which $\ce{NH3}$ is an example of), we see that these are the symmetry elements ${E, 2 C_3, 3 \sigma_v}$ present in the molecule. ...
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Solution of the Roothaan Equations of H2 by Symmetry Arguments
FWIW my background is in physics and maths, but I am just starting a chemistry PhD (the last time I took a chemistry class was high school). I have only some background in representation theory, and ...
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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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A question about rotational symmetry of organic molecules and in particular, the cyclic Isomers of C3H4X2
I was thinking about an organic chemistry problem a few days ago but reached a dead end. There were 2 parts to this question.
The first was thinking about the isomers of 'C3H4X2' [where X could be ...
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Optical activity of tartaric acid
The meso-form of tartaric acid is optically inactive due to the plane of symmetry. But how are these forms able to show optical activity when the σ-bonds can freely rotate, which can change the ...
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Is there a better coordinate framework and symmetry operator for constructing molecular orbitals of molecules with higher-order geometry?
The following excerpt is taken from [1] (with a few rewording, emphasizes are mine).
In an attempt to construct molecular orbital (MO) of any molecule, one needs to determine the symmetries of ...
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Tetrahedral complex and vibronic coupling or different rule for d-d transition?
I'm currently preparing a few slides for an upcoming talk in our group. I would like to mention some of the very basics regarding crystal field and ligand field theory as well, though this will not be ...
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Conventional unit cell for a hexagonal crystal system
The figure shows a unit cell of a hexagonal crystal system. Drawn in bold, is the unit cell. The lightly shaded one is a unit cell as well and has a six fold symmetry along an axis, hence is more ...
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