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.

Filter by
Sorted by
Tagged with
1
vote
0answers
50 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 ...
6
votes
0answers
387 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) ...
3
votes
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 ...
-1
votes
1answer
164 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 ...
7
votes
1answer
725 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 ...
1
vote
2answers
518 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, ...
-1
votes
1answer
414 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 ...
3
votes
1answer
633 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 ...
0
votes
1answer
1k views

Ethylene hybridization [duplicate]

In the carbon atom, there are electrons in 2s, 2Px, 2Py, and 2Pz. Out of these orbitals, only 2Px, 2Py, and 2s are hybridized. The 2Pz orbital is left. When making a bond there is a pi bond between ...
1
vote
2answers
145 views

CO₂ molecule π bonds [closed]

Why does $\ce{CO2}$ make two π bonds? Why can't it make four σ bonds? Also, why do the π bonds not involve for repulsion?
8
votes
1answer
524 views

Has it been observed that the dihydrogen molecule dissociates into ions?

As we know from the improved methods valence bond theory (VB), as well as molecular orbital theory (MO-LCAO), the wave function of the $\ce{H2}$ molecule consist of two terms, which belong to covalent ...
2
votes
0answers
2k views

Why is the nitrile nitrogen sp hybridized?

This site, from which the above image was taken, indicates that the hybridization of the orbitals on the C and N atoms in hydrogen cyanide is sp. I can certainly see how that would be the case for ...
1
vote
2answers
5k 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?
13
votes
3answers
962 views

Do Li4 or Li8 molecules exist?

I've read that alkali metals form ionic bonds; $\ce{Li}$ is an exception which majorly forms covalent bonds. Wikipedia says dilithium exists. This makes me wonder why $\ce{Li_8}$ doesn't exist. It ...
1
vote
2answers
968 views

Which overlap is stronger, and why?

I was just wondering which overlap is stronger, 2s-3p or 3s-2p? I believe this can probably be explained by involving some sort of mathematics (?) which I haven't used yet. Edit: Note that 2s-3p ...
0
votes
1answer
685 views

Why 2p Orbitals overlap more effectively than 3p orbitals?

So, for example, looking at HF and HCl, we see that the 1s orbital of the H overlap with the 2p orbital of F more effectively. Which argument can i use to explain that? Density?
-3
votes
2answers
129 views

Using the TLV, how do i explain that the HF has a stronger bond than HCl? [closed]

I know that both of them are sp3, and that the bond is formed by the overlap of the Pz sub-level with the 1s H. But, knowing this, how i explain the fact that HF has a stronger bond? Can i use ...
1
vote
0answers
144 views

How do we explain shapes of molecules using molecular orbital theory or do we even do that?

How do we explain shapes of molecules using molecular orbital theory or do we even do that ? While reading about the theories to explain chemical combination and stabilities of compounds I read ...
2
votes
0answers
1k views

length of bond, bond angle and p character in bond

My reference data: http://www.rsc.org/suppdata/ra/c4/c4ra06781a/c4ra06781a1.pdf Consider these five chemicals: A: $\ce{CH4}$ (methane) B: $\ce{CH3Cl}$ (chloromethane) C: $\ce{CH2Cl2}$ (...
1
vote
1answer
1k views

Difference between valency and oxidation state

I know the abstract and sketchy obscure differences but I cannot find anywhere the specific comparison between the concepts of oxidation states and valency including how they are used to describe ...
3
votes
1answer
2k views

Why does the energy required to break a bond decrease as the number of bonds increase?

I noticed that the energy to break a single C bond is $348\ \mathrm{kJ}$, to break a double C bond would be $612\ \mathrm{kJ}$, and to break a triple C bond would be $837\ \mathrm{kJ}$. How come the ...
6
votes
2answers
2k views

How are the hybrid orbitals of sulfur hexafluoride shaped?

On the fluorine end the fluoride atoms are simply completing a $3p$ orbital. On the sulfur end one could posit a hybrid of one $3s$ orbital, two $3p$ orbitals and a three inner $2p$ orbitals. However,...
1
vote
1answer
804 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 ...
6
votes
1answer
220 views

If I can't draw resonance structures for a pi system, does that mean it doesn't exist?

Whilst trying to answer this question I came across an interesting situation regarding the relationship between resonance structures and molecular orbitals. There are two places that you can ...
34
votes
4answers
4k views

What is resonance, and are resonance structures real?

My teacher told me about resonance and explained it as different structures which are flipping back and forth and that we only observe a sort of average structure. How does this work? Why do the ...
-1
votes
1answer
8k 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 ...
1
vote
0answers
538 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 ...
0
votes
0answers
585 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 ...
2
votes
1answer
754 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 $\bf{between}$ ...
0
votes
1answer
238 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 ...
1
vote
1answer
320 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 ...
1
vote
1answer
853 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 ...
2
votes
1answer
117 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 ...
5
votes
0answers
9k views

How does VB theory explain the bond angles in SiO2?

Silicon dioxide has a huge variety of structures. Most of them have a tetrahedral $\ce{SiO2}$ unit cell — the $\ce{O–Si–O}$ angle is $109.5°$, accordingly. The VB/hybridization approach to this ...
0
votes
1answer
150 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 ...
6
votes
1answer
9k views

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 ...
7
votes
2answers
4k 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 ...
0
votes
0answers
327 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}...
1
vote
1answer
552 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 $\ce{H2}$?
1
vote
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 ...
7
votes
3answers
6k views

Does the shared electron in Covalent bonds revolve around nucleus?

We know that electrons are charges that revolve around the nucleus. Then, when in covalent bonds the electron is shared; does the electron obey the rule?
2
votes
1answer
714 views

Why does phosphorus give a free electron in silicon doping?

Extrinsic semiconductors are created by doping an intrinsic semiconductor; typically silicon is doped with phosphorus to create free electrons or boron to create "holes". In the case of phosphorus ...
2
votes
2answers
731 views

Covalent bonds other then 2-center, 2-electron bonds

I've heard of single bonds, double bonds, triple bonds, and quadruple bonds between two atoms, but in each of those bonds the two atoms contribute the same number of electrons from each of their ...
0
votes
0answers
429 views

Comparing bond lengths of a molecule using valence bond theory?

My textbook says that all the bonds of $\ce{SF4} $ are not equal while in the case of $\ce{XeF_2}$, $ \ce{BF4-} $ or $\ce{SiF4} $ all the bonds are equal. No reason is stated for this observation. ...
7
votes
2answers
890 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 ...
1
vote
1answer
5k 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 ...
20
votes
1answer
210 views

Similarities and Differences between Resonance and MCSCF treatments

Recently, there has been a question by Voldemort concerning different resonance structures of $\ce{NCO-}$, requesting an explanation why one resonance structure would be more preferred than another. ...
8
votes
2answers
1k views

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"? (...
32
votes
3answers
19k views

What is actually the difference between valence bond theory and molecular orbital theory?

Recently I have read about both of the concepts in my book (Physical Chemistry by Atkins, Paula). It was literally a reading; though I could understand the language and superposition of orbitals, ...
3
votes
1answer
3k views

What Causes Atomic Orbitals to Hybridise?

I'm finding it difficult to visualise the process of hybridisation. Taking the example of formation of $\ce{CH4}$, can it viewed as the collapsing of the p orbitals of the Carbon atoms as they get "...