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
34k views

Why an asymmetric geometry with sp3d and sp3d3 hybridization?

A molecule in which the central atom is $sp^3d^2$ hybridized ($\ce{SF_6}$), for example, acquires an octahedral shape, which can be explained by assuming that the hybrid orbitals arrange themselves to ...
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3answers
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How can I derive the preferred oxidation states of a transition metal from its electronic configuration?

For example $\ce{Fe}\ (Z=26)$ Short formula: $\mathrm{1s^2\ 2s^2p^6\ 3s^2p^6d^6\ 4s^2}$. If we make the electronic formula we get 4 single electrons ($s=1/2$), which means that the valence in normal ...
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2answers
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What is Bent's rule?

I'm all bent out of shape trying to figure out what Bent's rule means. I have several formulations of it, and the most common formulation is also the hardest to understand. Atomic s character ...
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1answer
7k views

Hybridization of oxygen in Nitrate ion and the location/bond of nitrogen's lone pair

I have tried to apply the rules and basics that I learnt so far. But I am confused about the hybridization of oxygen atoms which are making the single bond in nitrate ion. Following are the steps I ...
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1answer
1k views

Why does greater orbital overlap mean a stronger bond?

According to valence bond theory, orbital overlap produces a bond. However, I don’t understand why having greater orbital overlap renders a bond stronger. It’s intuitive, I suppose, but I haven’t been ...
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2answers
961 views

Why is sulfur dioxide more stable to UV radiation than ozone?

Ozone readily decomposes when impacted by UV radiation. Sulfur dioxide, having the same bond structure and valence electrons in each atom as ozone, is much more stable. Would someone please help ...
8
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1answer
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What holds atoms together? [duplicate]

I know atoms are held together by Ionic and Covalent bonds and i understand the ionically bonded atoms are held together by electrostatic forces. What about covalent bonds? How are molecules of bonded ...
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1answer
10k views

Why does Sulfur have 12 valence electrons in the Sulfate ion? [duplicate]

So I am completely and utterly confused about why sulfur has 12 valence electrons. I understand in it's configuration, it has 2 electrons for the 3s subshell, and 4 electrons from its 3p subshell, and ...
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1answer
2k views

What is the highest possible expanded octet?

Often called "hypervalent", chemicals like phosphorous pentachloride and sulfur hexafluoride are possible due to the fact that their central atoms form covalent bonds with more than four other atoms, ...
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0answers
684 views

Why Don't Sulfur Atoms Hybridize?

I am doing some chemistry problems with given answers, and supposedly the $107^{\circ}$ and $92^{\circ}$ bond angles in $\ce{H_2O}$ and $\ce{H_2S}$, respectively, is due to the fact that"$\ce{O}$ uses ...
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688 views

Why are hybrid orbitals more efficient at overlapping?

What is the reason for considering that hybrid orbitals provide more effective overlapping resulting in formation of stronger bonds? Will this reasoning be correct that the hybrid orbitals have ...
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1answer
92 views

My text seems to say that the high(est) energy orbitals are not valence orbitals - everything else says otherwise. What's true?

A paragraph in my text reads Bonding involves the valence orbitals almost exclusively because these orbitals have the appropriate energies to interact strongly. Examine the electron energy-level ...
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1answer
1k views

Delocalised electron in graphite

I have a question regarding the delocalised electron in graphite. There has been conflicting information between books. Some books said the delocalised electron in graphite exists $\bf{between}$ ...
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1answer
270 views

Radicals' formation

If carbon atom is tetravalent while oxygen atom is divalent so when they combine together the result should be $\ce{C2O4}$ then how are there compounds of formulas with $\ce{CO2}$, $\ce{CO3}$ and ...
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1answer
390 views

Why do atoms bond? Why are unfilled valence shells energetically unstable? [closed]

I teach school Physics. And am trying to get a reasonable explanation of the root cause of the energetic instability of unfilled outermost electron shells that leads to atoms bonding. For most of what ...
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1answer
1k views

Relation between various bond angles of Nitrogen compounds

I was thinking what could be order of bond angles of NH3, NF3, N(CH3)3 and N(C2H5)3. Considering NF3 and NH3: Since there is backbonding between 2p-2p orbitals of N and F, there will be a partial ...
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1answer
125 views

How can anions exist?

Lets say we have an nitrogen atom - it should have 7 protons and 7 electrons. How can an nitrogen anion - lets say $\mathrm{N^{\,1\mathbf{-}}}$- even exist - shouldn't the 7 electrons in valence ...
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1answer
183 views

'In MO theory, electrons are treated as spreading throughout the entire molecule'- isn't it exhibited in VB theory also?

First statement: In the molecular orbital theory, the valency electrons are considered to be associated with all the nuclei in the molecule. - Concise Inorganic Chemistry by J.D.Lee. Second ...
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1answer
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why do electron pairs not take axial positions in the VSEPR structure of ClF3? [duplicate]

when we make a Valence shell electron pair repulsion theory based structure for an molecule after calculating its hybridisation ; when we have to decide the positions of the ions we put them in such ...
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2answers
5k views

Hybrid orbitals forming molecular orbitals

My teacher showed me this diagram on how the hybrid orbitals of two atoms combine to form molecular orbitals. I was confused by this because I thought that VB and MO theories were two separate ...
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0answers
1k views

S-O bond length in SO2 and SO3 [duplicate]

Question: which molecule out of $\ce{SO2}$ and $\ce{SO3}$ has larger $\ce{S-O}$ bond length? Both are $sp^2$ hybridised. Since $\ce{SO3}$ has more bond pair - bond pair repulsions, shouldn't $\ce{SO3}...
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1answer
977 views

What properties of an element determines the maximum number of bonds it can make?

From my conjecture, I think it's a mix between valence electron and the principal energy state, but I'm not sure. For example, C, N, O and F can only make a maximum of four bonds, as they can only ...
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1answer
938 views

Physical Meaning of the Difference between MO and VB Wave Function of H2?

What would be the physical meaning of the difference between the MO wave function and VB wave function of $\ce{H2}$?
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3answers
559 views

How many coordinates should be used for the potential energy surface of a non-rotating linear molecule? (3N-6) or (3N-5)?

Take, for example, $\ce{CO2}$. It is pretty clear that in the absence of rotation, the energy of this system depends only on the two bond lengths and the bond angle. So if I wanted to build a ...
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1answer
454 views

2p Orbital Occupancy

What does the question mean by how many electron pairs are in 2p orbitals? How does one tell? Given that both the oxygen and the nitrogen are $\ce{sp^2}$ hybridized, wouldn't there be two 2p orbitals?
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Resonance - Legal Moves

My teacher insists that we can push electrons either from a bond to an atom's valence, or vice versa. Bond to lone pair; lone pair to bond, he insists. However, what about bond to bond? Is there a ...
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1answer
2k views

How to calculate bond angle of simple molecules quantitatively?

Hi I'm new to this forum so spare me if I've made mistakes. Our high school chemistry teacher explained that bond angles of different molecules varies slightly, e.g. 107 degrees in ammonia and 104.5 ...
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1answer
315 views

Orbital Electronegativity Considerations in Resonance Structures

After consulting three organic chemistry texts (Wade, Klein, and Brown), only one actually clearly delineates a few guidelines for picking the most significant resonance structure. The others mention ...
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1answer
179 views

Electronic model with highest prediction rate

Amongst 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 ...
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1answer
56 views

Why V can't have the valence 7 by taking an electron from the 3p orbital and putting it into 3d?

Does that happen because 3p already has a bond?
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2answers
2k views

What does it mean when it is said that an sp³ orbital has 25% s character?

My textbook frequently mentions: $\mathrm{sp^3}$ hybrid orbital has 25% $\mathrm{s}$-character and 75% $\mathrm{p}$-character. What are these "characters"? And how do these characters influence ...
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2answers
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Why is the resonance concept not required in molecular orbital theory?

In valence bond theory, resonance plays a pivoting role; why isn't such concept needed in MO theory? Why is it told that "MO theory provides a global, delocalized perspective on chemical bonding"? (...
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2answers
151 views

Why does an element's chemical properties rely only on its valence electrons and not on anything else?

I understand that elements use their valence electrons for their reactions and whatnot, and that the whole idea of the electron-dot structure is all about valence electrons. But why can't the other ...
4
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1answer
427 views

Bonds and pairing of spins

I was reading Peter Atkins' Elements of Physical Chemistry where I came across this line: Bonds do not form because electrons tend to pair; bonds are allowed to form by the electrons pairing their ...
3
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1answer
11k views

Why are the axial bonds of PF5 longer than those of the equatorial bonds? (Hybridization) [duplicate]

The axial bonds of $\ce{PF5}$ are longer than those of the equatorial positions. One explanation is that because the axial bonds are experiencing more repulsion than those of the equatorial and ...
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1answer
671 views

Order of priority in hybridization of d-orbitals

During hybridization of d-orbitals why the $d_{z^2}$ and $d_{x^2-y^2}$ orbitals are used up before the $d_{xy}$, $d_{yz}$ and $d_{zx}$ ?
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3answers
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Why does Pb normally have an oxidation number of +2?

Why does $\ce{Pb}$ have an oxidation number of $2^{+}$ while carbon and other elements in the same group have an oxidation number of $4^{+}$? Furthermore, why doesn't carbon also have a $2^{+}$ ...
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1answer
2k views

How does CrF₆³⁻ hybridize?

My textbook says that $\ce{[CrF6]^{3-}}$ is an example of $sp^3d^2$ hybridization. But I don't really see how. Chromium has an electronic configuration of: $$3d: \boxed{\uparrow}\boxed{\uparrow}\...
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1answer
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Structure of benzene

How does molecular orbital or valence bond theory explain the delocalised structure of benzene? I.e. when the carbon forms 3 bonds with other carbons/hydrogen, what happens to the remaining hybridised ...
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1answer
746 views

How to find the possible valence states of elements in the lower end of the d block and the f block?

For silver, why don't the electrons in the 4d orbital move to the 5p orbital? Is it possible for any elements to move their electrons between $n$d and $(n+1)$p orbitals? When the f orbital is ...
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2answers
5k views

Why do unbonded electrons exist in pairs?

Basically the term which we use to refer them is lone pair. In Lewis structure why we represent those unbonded electron in pairs. Like here (structure of SO2) Here if we assume both the unbonded ...
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0answers
88 views

Explanation of Bent's Rule [duplicate]

Why does the %s character increase on the orbital with electropositive atom? I do not seem to properly grasp this concept. Is this rule based on observation or is there any proof to it? If there is a ...
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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 ...

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