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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6
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1answer
79 views

How are the energies of natural atomic orbitals calculated when they are, strictly speaking, not "meaningful" wavefunctions?

There are several programs that can calculate the "energies" of the natural atomic orbitals(NAO) that come from NBO analysis. However, I have several evidence that, unlike the energies of ...
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28 views

Question on relativistic treatment of the "classical" sp² hybridisation

Let there be a single molecule of boron trifluoride, happily floating in the vaccum. Also let the unfilled p orbital on the central boron be the 2pz orbital. Then, the 2s, 2px and 2py orbitals are ...
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1answer
123 views

Justification for using valence bond theory and molecular orbital theory together?

Elementary gen chem books will make the careful distinction between the two theories and then proceed to claim that chemists can use both to complement each other to explain the behavior of certain ...
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1answer
208 views

How to determine the shape of hybridized atomic orbitals in VB theory?

From diagrams, it's rather obvious how $sp$ orbitals are hybridized - the hybrids are just a composite of the $s$ and the $\pm p_{(x)}$ orbitals. However, $sp^2$ orbitals are not just composites of $s,...
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1answer
53 views

What is the best way to visualize hybridization [closed]

I had learnt hybridization in various complex definitions some of them as "complex overlapping of orbitals (in quantum mechanical model) which leads in changing of shape of orbitals itself. But ...
1
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1answer
69 views

Why is the Br-C-H bond angle in CH3Br smaller than the Cl-C-H bond angle in CH3Cl?

Can someone explain for me why the Br-C-H bond angle in CH3Br is smaller than the Cl-C-H bond angle in CH3Cl? From what I know, F-C-H in CH3F has a smaller bond angle than Cl-C-H in CH3Cl because F is ...
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0answers
42 views

Distribution of Valence Electrons [closed]

I'm fairly confused over just how electrons are distributed in a molecule according to the lewis structure. The octet rule states that atoms have a tendency to have 8 electrons in their valence shell. ...
1
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1answer
88 views

Comparing strengths of σ-bonds formed by $\mathrm d_{z^2}$ and $\mathrm p_z$ orbitals

According to my professor $\mathrm d_{z^2}–\mathrm d_{z^2}$ σ-bond is stronger than $\mathrm p_z–\mathrm p_z$ σ-bond as the extent of overlapping is greater in $\mathrm d_{z^2}–\mathrm d_{z^2}$ ...
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61 views

Why is maximum number of covalent bonds 3? [duplicate]

In my textbook it is mentioned that maximum 3 covalent bonds can be formed within 2 atoms, which makes sense as 1 p orbital from each can be used for sigma bond and the remaining 2 can form pi bonds. ...
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35 views

Does overlapping partial density of states indicate formation of chemical bond?

Does overlapping partial density of states of two adjacent atoms indicate formation of chemical bonds between the two atoms? The partial density of states here means the density of states of an ...
2
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1answer
243 views

Why does this ligand form 6-coordinate complexes with Transition elements and 8-coordinate complexes with Inner transition elements? [closed]

The ligand given above shows different denticities with common transition and inner-transition metal ion i.e. 6 and 8. The extra two denticities come from the two Nitrogen having 1 lone pair each. I ...
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1answer
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Manganese and valence layer [closed]

Why does manganese make $4$ bonds in $\ce{H_2MnO_4}$ when it has only two electrons in the valence shell?
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51 views

Hybridisation of Azide ion

In azide ion, $\ce{N3-}$, the hybridisation is $\mathrm{sp}$ because number of hybrid orbitals = steric number, the central atom $(\ce{N})$ has 6 bonds with other $\ce{N}$ atom, 2 of which are sigma ...
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443 views

Why do the d orbitals contract when pairing of electrons start, because the size should increase due to increase in energy

The energy of an orbital is proportional to its mean radial distance, and since the 3d orbital is much larger it is much higher in energy than the 3s and 3p orbitals All references from JD Lee ...
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1answer
76 views

Role of 'p' Orbitals in Graphite Carbons

In the graphite arrangement of carbons, if we model them according to hybridization theory, the carbons in graphite are sp2 hybridized. This would mean that one s and two p orbitals hybridize, making ...
0
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1answer
310 views

Why does the Lewis structure for NH2 have 4 dots and not 3? [duplicate]

Nitrogen has 5 valence electrons. So I would expect that when bonding with two hydrogens, two electrons would go into those bonds, and three would remain in place on the nitrogen. Yet, all the ...
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33 views

Which forms the stronger sigma bond- s-s overlap or p-p overlap? [duplicate]

I'm asking this question as I hear arguments for either. For s-s bond being stronger, I was told that because both are spherical, overlap can occur in any plane- a lack of directionality gives more ...
7
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1answer
235 views

How to compare magnetic moment of chromium(III) and cobalt(II) ions?

Is there any way of comparing the magnetic moments of $\ce{Co^2+}$ and $\ce{Cr^3+}$ gas phase ions by just going through their electronic configuration?Or is it just experimental data?
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3answers
9k views

Why are pi bonds only formed when sigma bonds are formed?

While studying about bonding there was one statement that "pi bonds can only be formed only with sigma bonds" as we know that in double bond there is 1 sigma bond and 1 pi bond but then one question ...
3
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71 views

Why is the bond angle of sulphur difluoride greater than that of hydrogen sulphide?

Why is the bond angle of $\ce{SF_2 (98.05^\circ) > SH_2 (92.11^\circ)}$? Isn't this contradicting Bent's rule or otherwise electron repulsion rule ? Fluorine is more electronegative and hence it ...
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0answers
386 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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0answers
86 views

How are 3 center-4 electron bonds any different from 2 center-2 electron bonds? [closed]

How are the bridge bonds in $\ce{Al2Cl6}$ different from the terminal bonds? We could have just mentioned the bridge bond formed by $\ce{Cl}$ as a coordinate bond. Why introduce this extra concept? I ...
13
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1answer
9k views

Delocalization of π-electrons in nitrate ion

Benzene and nitrate ion are given in my textbook as examples for the delocalization of π-electrons. Benzene, due to symmetry of its resonating structures, is simple enough. We assume that σ-electrons ...
2
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0answers
97 views

Why does NH3 cause pairing in case of some metal complexes and doesn't in case of others?

I was met with a question that required me to find which complex is an outer orbital complex, and two of the options included $\ce{ [Ni(NH3)6]^2+}$ and $\ce{[Co(NH3)6]^3+}$, I want to know why does $\...
2
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0answers
91 views

Application of statement: extent of overlapping is always less than 50% because of electronic repulsion [closed]

Question from the online class: Can two s-orbitals overlap as shown? Dotted circles in diagram depict maximum probability region of s-orbitals in ideal situation when atoms A and B are not bonded. ...
3
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2answers
425 views

Explain on the basis of valence bond theory that tetracyanonickelate(II) ion with square planar structure is diamagnetic

Answers on the internet suggest that tetracyanonickelate ($\ce{([Ni(CN)4]^{2-}}$) with square planar structure is diamagnetic because $\ce{CN-}$ is a strong field ligand and causes pairing, but my ...
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2answers
1k views

How to find the valence of transition elements?

Let's take Iron for example As we can see there are 4 desolate electrons in normal state. Can you tell me which electron moves to make the valence 2 and then 3. We have learnt to find the valence ...
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1answer
72 views

Hybrid lobes of sp3d2 and sp3d3 [closed]

It's known that $\ce{sp^3d}$ hybridization has 5 lobes; 3 equatorial with $\ce{sp^2}$ lobes and 2 axial with $\ce{dp}$ lobes. Do we have such splitting in $\ce{sp^3d^2}$ and $\ce{sp^3d^3}$ ...
7
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2answers
225 views

Hypervalency of orthonitrate

I have always believed that it is impossible for the atoms of period 2 elements (when they are the central atoms in polyatomic ions/molecules) to accommodate more than 8 electrons in their valence ...
2
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1answer
8k views

What is the maximum covalency of oxygen?

My text says it to be 4. I believe it's 2. Is there any compound where covalency of 4 is observed?
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1answer
75 views

Why is it that nitrogen hybridizes in ammonia, yet in F2, fluorine does not [closed]

It seems rather arbitrary to me that we have decided that nitrogen sp3 hybridizes in ammonia to stay consistent with VSEPR, yet that fluorine uses its 2p orbital to bond with another fluorine in F2 (I....
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2answers
55 views

do electrons in different orbitasl in a same subshell have same energy

In valence bond theory, I suppose that electrons in say, 2px and 2py have the same energy because of the same structure of orbitals. But what about 3dxy and 3dz^2? Do they also have the same energy? I ...
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1answer
91 views

What is the difference between resonance and π conjugation

I have seen electron delocalization mentioned frequently in 2 separate contexts: resonance (ozone, carbonate / nitrate...) and π-conjugation systems (aromatic compounds). While the 2 initially sound ...
3
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2answers
218 views

Why does delocalization (only) occur in molecules represented by resonance hybrids?

Before I start this question, I am aware tha Electrons in all molecules are delocalized to some extent Delocalization is a the phenomenon and resonance is an attempt to explain it. When I asked this ...
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0answers
34 views

is there a stead fast rule to predict hybridization or is it just an ad hoc concept

Before I start of this question, Ι want to make it clear that I know that hybridization, like pretty much all of chemical bonding, are just made up to qualitatively rationalize observations. I know ...
2
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2answers
118 views

Insight into covalent bonds from electrostatic perspective

I try to understand, from the electromagnetic side only, how the molecule could be more stable than each atom, and concluded that it could not. Where is my mistake? Here is an illustration : By using ...
2
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0answers
45 views

what does "overlapping" of orbitals mean and why does it effect bond strength(VBT)?

according to valence bond theory, bonds are formed due to the pairing of unpaired valence electrons due to the overlap of half-filled orbitals, and the strength of the bond depends on the extent of ...
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36 views

Direction of valence bond and Unsöld's theorem

Is it true that the atomic orbitals of separate atoms already have directionality, which ensures the directionality of the valence bond? Or another words, what is the real spatial distribution of the ...
17
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1answer
11k views

How does VB theory explain the Si-O-Si bond angles in SiO2?

Silicon dioxide has a huge variety of structures. Most of them are built up from connected $\ce{SiO4}$ units — the $\ce{O–Si–O}$ angle is $109.5°$, accordingly. The VB/hybridization approach to this ...
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2answers
206 views

Why there is no sp2s hybridization in hydrocarbons? [closed]

If carbon's $\mathrm{sp^2}$ orbital is overlapped with hydrogen's $\mathrm{s},$ then why it is $\mathrm{sp^2}$ and why not $\mathrm{sp^2s}?$
3
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1answer
297 views

Which combinations of orbitals lead to pi bonds according to Valence Bond Theory?

How many of the following combination of the orbitals will lead to formation of $\pi$-bonds with $z$ axis being the internuclear axis: $$p_x+p_x,\,p_z+p_z,\,p_y+p_y,\,d_{zx}+p_x,\,d_{zy}+p_y,\,s+p_y,\,...
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2answers
99 views

Transition metals with closed shells

From wiki page about valence electrons: An atom with a closed shell of valence electrons (corresponding to an electron configuration $s^2p^6$ for main group elements or $d^{10}s^2p^6$ for transition ...
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0answers
124 views

Misconception in valence bond theory

Since the overlap increases with directional properties of orbital, $$\ce{p - p > s - s > s - p}$$ However it is also observed that the bond strength of $$\ce{H-F > H-H > F-F}$$ $$\ce{\{s ...
3
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3answers
193 views

Effect of magnetization on oxidation (rusting) of iron

Can magenetizing a piece of iron bar slow-down (or speed-up) the oxidation (rusting) process? In other words have any influence on it ? From what I've looked up( wikipedia, quora), it appears that the ...
64
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1answer
10k views

Why does F replace the axial bond in PCl5?

Why does $\ce{F}$ replace an axial bond in $\ce{PCl5}$? I realize that it would be more stable there than at equatorial bond, but what is the reason of its stability? Similarly in $\ce{AB4}$ type of ...
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0answers
277 views

Comparison between Molecular Orbital Theory and Valence Bond Theory

I have been reading about introductory Molecular Orbital Theory lately. Till now, I have used Valence Bond Theory to evaluate bonding. I have a few questions about it:- In VBT, we used the idea that ...
4
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1answer
27k views

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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1answer
53 views

Why isn't just a fully occupied valence s orbital stable?

Why arent elements like calcium with an electron configuration of $[\text{noble gas}]\ n\mathrm{s}^2$ stable, although all the populated orbitals are fuully filled? Why is it necessary to obtain an ...
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1answer
1k views

Maximum number of coplanar atoms in difluorotrimethylphosphorane

In $\ce{PF2(CH3)3},$ what is the maximum number of atoms lying in one plane? $\ce{P}$ is the central atom with the hybridization $\mathrm{sp^3d}.$ Two $\ce{F}$ atoms will form axial bonds with it, ...
3
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2answers
747 views

Comparing bond angles in carbonyl dichloride and carbonyl dibromide

Background I was studying VSEPR and hybridization theory and one of the popular questions in many textbooks was comparison of bond angle of $\ce{NH3}$, $\ce{NF3}$ and $\ce{NCl3}$. $\ce{NF3}$ had ...