Questions tagged [valence-bond-theory]
Questions about how the atomic orbitals of the dissociated atoms combine to give individual chemical bonds when a molecule is formed.
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Bond dissociation energy among halogens
Among the halogens, why is it that the fluorine has the lowest bond dissociation enthalpy, considering the fact that fluorine is the smallest and the internuclear distance between the fluorine ...
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23 views
How one can calculate Si-O-Ca/Mg valence angle energy?
I want to perform the relaxed scan (or relaxed surface scan) for the valence angle energy of Si–O–Ca, Si–O–Mg, Al–O–Ca, and Al–O–Mg. I will use DFT (ORCA), probably B3LYP and triple zeta basis set (...
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38 views
Reason behind hybridisation [duplicate]
I have been taught that orbitals can overlap only when all of them are in the same energy state. That is the reason why the orbitals hybridise in a kind of 'mixing up' and give rise to orbitals having ...
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2answers
107 views
Is dihydrogen the only example of overlap between two s orbitals?
I heard that $\ce{H2}$ is the only example of s–s orbital overlap. Can anyone give an example which contradicts this statement?
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25 views
Can 2 dz2 orbitals form a π bond?
Usually , d orbitals overlap sideways along a common internuclear axis, but drawing and checking for dz2 , it always seems to form a sigma bond or null overlap.
Is this because it doesn't have any ...
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40 views
Why are d(xy),d(yz) and d(xz) orbitals involved in d³s hybridisation?
Shouldn't d(x²-y²) dxy and dz² orbitals participate? Since this corressponds to the best case overlap?
What factors decide the participating orbitals in hybridisation?
P.S I am well versed with the ...
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1answer
41 views
Doubt regarding timeline of events and development of theories
I recently studied Zaitsev's and Hoffman's rules for deciding which product is formed via elimination and noticed that the rules for formulated much before the discovery of electrons and any ...
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1answer
61 views
Why is $1s-1s$ orbital overlapping stronger than $2p_x-2p_x$ orbital overlapping?
Assume the x-axis to be the internuclear axis. Hence, both $1s-1s$ and $2p_x-2p_x$ will form $\sigma$ bonds.
Also consider the fact that $p$ orbitals have more directional characteristics.
Given the ...
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47 views
Why is it not possible for seven close copper atoms to come together to gain a noble-gas configuration of valence electrons?
My textbook says the following about metallic bonding:
The metal copper has one valence electron. The valence electrons of nearby copper atoms are shared in a similar way to covalently bonded ...
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44 views
How to Choose Orbitals for Hybridization
Recently, I was reviewing my textbook regarding orbital hybridization, and one of the problems was to determine the hybridization of each of the atoms in $\text{CO}_2$. I understand why the ...
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1answer
34 views
Periodic Table and Atomic Radius
Well Wikipedia says that the atomic radius is lowered for elements in a group closer to noble gases (same row). It also says that those elements want to keep their valence electrons more than metals, ...
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1answer
35 views
Electric conductivity
Well I was wondering why some materials have a higher resistivity than others . So I took two elements randomly . I picked carbon and silicon . Carbon has lower resistivity than silicon and obviously ...
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281 views
Valence bond theory and molecular orbital theory — how do they complement one another?
Based on my readings, valence bond theory (VBT) and molecular orbital theory (MOT) tend to complement one another in explaining a molecule, but I don’t understand how VBT helps us explain the ...
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207 views
How do I explain these bond angles in SF4 and SOF4?
From here and here I found that the bond angle between the equatorial $\ce{F}$'s in $\ce{SF4}$ is less than that in $\ce{SOF4}$. I understand that is because of greater repulsion by lone pair than by ...
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1answer
240 views
Why does NH3 hybridize at all?
So in Chemistry class I've been taught that hybridization is a way we can explain things such as how $\ce{CH4}$, for example, forms four, equally strong bonds.
However at the same time I'm told that ...
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1answer
90 views
Why is a carbon to iodine pi-bond less stable than a carbon to fluorine pi-bond?
This question comes from a second semester undergraduate organic chemistry course. Please refer to the image below with regard to the question.
My understanding of the trend in section 4a is that "...
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1answer
104 views
Reason for shorter bond between sulphur and oxygen?
I recently came across this sentence in my textbook “the bonds between sulphur and oxygen in oxides of sulphur (SO2 and SO3 ) are much shorter than might be expected for a single bond”
SO3
I feel ...
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1answer
183 views
Why is carbon monoxide a monodentate ligand
Carbon monoxide has lone pairs on both the carbon and the oxygen atoms. However, I have never seen any complex where the oxygen atom or both the oxygen and the carbon atoms are the donors.
I know ...
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0answers
68 views
Dichlorine monoxide molecular geometry
I need to predict the geometry of Dichlorine monoxide, using the main link theory: Lewis model, VSEPR and hybridization of molecular orbitals.
First, the Lewis structure is a graphical representation ...
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1answer
1k views
Bonding in Zeise's salt
I am not sure I completely understand the bonding in coordination compounds formed by donation of pi electron cloud by the ligands to the central atom.
For example, consider Ziese's salt:
I came ...
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1answer
87 views
How many equal Xe–O bond length are present in (XeO_6)-3? [closed]
I tried to solve this problem by drawing a structure but the structure did not give me any answer and I was not able to draw the proper structure please help me out.
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0answers
21 views
Why does aluminum in zeolites form tetrahedras? [closed]
It forms a bond with four oxygen atoms even though it has only there electrons in his outter shell?
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1answer
66 views
Molecular Geometry [duplicate]
Why is it that for a molecule with trigonal bipyramidal geometry, the lone pair is located in the equatorial region whereas for a molecular with an octahedral geometry, the lone pair is located in the ...
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1answer
642 views
Graphite: Thermal and electrical conductivity
I recently encounter this question:
Compare, while providing an explanation, the thermal and electrical conductivity of graphite to that of diamond.
Provided answer:
Graphite conducts electricity(...
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0answers
161 views
The nature of Chemical Bonds [closed]
It was nearly a year ago when I appeared for my first interview through the KVPY (a research oriented scholarship exam) when one of the questions the panel asked me was :
What is a chemical bond?
...
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1answer
1k views
Ionization energy of C2-, C2, and C2+
My textbook says that $\ce{C_2}^-$ has a lower ionization energy than both $\ce{C_2}$ and $\ce{C_2}^+$. I calculated that the bond orders of $\ce{C_2}^+$, $\ce{C_2}$, and $\ce{C_2}^-$ are 1.5, 2, and ...
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280 views
Why is octet extra stable? [duplicate]
In chemistry, it is agreed in general that the octet is extremely stable, through experiments except in some cases. But is there any specific theoretical reasoning for that?
According to me, if:
...
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113 views
Why don't I get the same value of percentage ionic character of a particular molecule from different equations?
About the ionic character of a polar covalent compound Pauling gave two equations as
[1-$e^{.25(x_a - x_b)}] $%
[18$(x_a-x_b)^{1.4}$]%
Hanary and Smith gave the equation
[$16(x_a-x_b)+3.5(x_a-...
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1answer
60 views
Using real wave functions for chemical bond explanation
My question related with another one here.
For explanation valence bond direction chemists are used real wave functions, for example $p_x, p_y, p_z, \ldots$. But this functions do not describe the ...
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1answer
645 views
Why do halogens have odd numbers as oxidation number?
Halogens like $\ce{Cl}$ always exhibit $+7,+5,+3,+1,-1$ as their oxidation numbers. I found the following answer after checking several sources:
Halogen atoms have $7$ electrons in their valence ...
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1answer
425 views
Why is the oxidation state of Carbon (-4)?
Based on my understanding, atoms try to achieve the electronic configuration of the nearest noble gas, by losing or gaining electrons. For example, Sodium is closest to Neon, so loses an electron so ...
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1answer
597 views
Where do the lone pairs go in the “true” resonance structure?
Consider the "true" resonance structure of $\ce{CO3^2-}$:
The bottom diagram leaves out the 2 lone pairs, so 4 electrons disappeared in the bottom image as compared to the top one. Are these ...
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1answer
587 views
Do 1s & 2s orbitals overlap of different atoms while forming sigma bond? I
Do 1s & 2s orbitals overlap of different atoms while forming sigma bond?
I think they should overlap as there will not be enough energy difference between them.
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1answer
324 views
Buckminsterfullerene double bonds [closed]
I am not now nor have I ever been a chemist.
I'm practicing by drawing molecules in the Chemspider structure search tool. Today I drew buckminsterfullerene, in order also to test my 3D spatial ...
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0answers
437 views
How to calculate steric number of methyl free radical?
According to the definition, steric number = number of atoms it is attached + lone pair.
In that way, I get 4 for methyl free radical which means sp3 hybridization . But that's wrong !
Why is this ...
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3answers
1k views
HCH bond angle in cyclopropane and cyclobutane
I understand why the $\ce{CCC}$ bond angles in cyclobutane and cyclopropane are less than ideal $109.5^\circ$ due to the geometric restrictions they encounter in a cyclic structure. However, it is not ...
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706 views
Why are d orbitals used in the hybridisation of PCl5 and similar compounds? [duplicate]
Phosphorus uses its $\ce{3s}$, three $\ce{3p}$ and one $\ce{3d}$ orbitals for its hybridization in $\ce{PCl5}$ and similar compounds.
However, shouldn't it use its $\ce{4s}$ rather than $\ce{3d}$ ...
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1answer
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How can the hybridisation schemes of transition metal complexes be determined?
Lets say I have to find hybridisation of $\ce{[Ni(CO)_4]}$ and $\ce{[Ni(CN)_4]^{2-}}$.
The metal atom/ion in these compounds are $\rm Ni$ and $\rm Ni^{2+}$ respectively.
So the outer shell ...
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0answers
154 views
The affect of effective nuclear charge on energy gap between subshells
A few days ago my teacher taught me about $\mathrm{d}$ orbital contraction. He said that in $\ce{SF6}$ the hybridization of sulphur is $\mathrm{sp^3d^2}$. He said that although the $\mathrm{d}$ ...
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1answer
295 views
Hybridisation and bond strength
I'm a high school student with minimal mathematical knowledge about the theory of chemical bond. (I just have a bit of theoretical background). I came across a statement which stated that "The more is ...
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3answers
5k views
Determining the structure of N2O using hybridization
I have learnt how to determine the structure of molecules where only the central atom is hybridised like $\ce{ClF3}$, $\ce{C2H2}$, $\ce{PCl5}$, but in $\ce{N2O}$ it seems as though both nitrogen and ...
3
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1answer
2k views
Valence Bond theory, VSEPR theory and predicting the shapes of the molecules
I read about the above mentioned theories then used them to predict the molecular geometry. However, I found that the shape/geometry of a molecule obtained from both the theories was same. For example,...
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0answers
43 views
How do delocalized π electrons satisfactorily fill π orbitals? [duplicate]
The above example is benzene.
Only six electrons contribute to the 6 π bonds and pπ orbitals. Normally, an orbital requires two electrons to satisfactorily "fill" it. I don't understand how this ...
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0answers
329 views
Chemical bonding with f orbitals
For the elements such as rhenium, osmium, iridium how probable is for electrons in the inner 4f orbitals to gain energy and take part in a molecular orbital (such as an $f^2 d^2 s p^3$ hybrid orbital) ...
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3answers
1k views
Inductive effect and bond strength
What is the relation between the inductive effect on bond length and strength.
how would one rank the bond strength of
$\ce{CH3-H}$, $\ce{CH3CH2-H}$, and $\ce{(CH3)2CH-H}$
I know that alkyl groups ...
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1answer
140 views
Ammonia sigma bonds p character
Why does ammonia's sigma bonds to H have more p character than let's say ethane.
I am guessing it has something to do with the effect the lone pair has on bond lengths and angles, but not quite sure ...
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1answer
666 views
How to explain molecular geometry without the help of VSEPR, valence bond, or hybridization theories?
I was taught, at the high school level, how to rationalise molecular geometries with the help of VSEPR, valence bond, and hybridization theories.
However, I have recently also come to know that these ...
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2answers
449 views
Structure of AsF3Cl2
Since the molecule has 5 bonding pairs and zero lone pairs, the shape should be trigonal bipyramidal. But one thing i am confused about is which atom(s) will occupy the axial and the planar positions, ...
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1answer
350 views
Confusion regarding sigma bond and pi bond
I was recently told that a sigma bond between two $\mathrm{3p}$ orbitals is possible but a $\pi$ bond between the same orbitals is not possible.
Although I was not told the reason, I am speculating ...
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1answer
591 views
Hybridisation and the Schrödinger equation
I am slightly confused about hybridisation and how it relates to molecular and atomic orbitals, despite having pored through many sources online. I was hoping someone could verify whether my current ...
