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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.

25 questions with no upvoted or accepted answers
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11
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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 ...
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422 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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58 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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436 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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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 ...
2
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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: $\ce{CH2Cl2}$ (...
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30 views

Is bonds in CO is all 3 coordinate bonds or 2 covalent and 1 coordinate bonds?

Below image is as available in India's Class 11 NCERT Chemistry book vol 1 Page 104. I am confused as it states all 3 bonds are kind of coordinate bonds. Should it not start with 2 covalent bonds and ...
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77 views

Why are sulfur trioxide and nitrate not isoelectronic, even though both have the same number of outer electrons?

Though $\ce{SO3}$ has the same number of outer electrons as $\ce{NO3-}$, the two are not isoelectronic. This statement is from JD Lee, but I could not understand why is he calling these two molecules ...
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0answers
34 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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105 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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0answers
511 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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169 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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153 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 ...
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565 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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48 views

Why does C=C bond replace C-O bond when two graphite platelets are rubbed against each other edge on edge?

When two small 2D carbon platelets are pushed into proximity, why do they release the edge attached molecule (maybe O) and then bond C to C? I think the answer I seek would address the relative ...
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1answer
617 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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1answer
88 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 ...
0
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30 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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152 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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79 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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57 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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149 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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600 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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432 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. ...
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42 views

Why N=N is much stronger than N—N but C=C isn't

Why N=N bond is much stronger than N—N bond (about 2.5 times) but C=C is not (less than 2 times)? IMO, the radius of nitrogen and carbon atoms play a big role here. Since rN < rC, the AOs creating ...