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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Magnetic nature of tetraamminedichlorocobalt(III) chloride

I know how to predict magnetic nature when the compound contains only strong field or only weak field ligands. But in $\ce{[Co(NH3)4Cl2]Cl},$ $\ce{NH3}$ is a strong ligand whereas $\ce{Cl-}$ is a weak ...
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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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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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What is the hybridization of chromium in chromate and dichromate ions?

I was recently reading about the transition metals and some important compounds of them. I came across a rather interesting diagram in my book... a tetrahedral structure for the chromate ion. The only ...
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Why is the valency of the Calcium (Ca) Bohr model, set to 2 electrons, instead of 1 electron for stability? [duplicate]

This is an Ascii table for the elements on the 4th period (row) of the periodic table, and distribution of electrons in each orbit. ...
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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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625 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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Bonding in the nitrate anion [duplicate]

Hi so I was studying chemical bonding where i encountered a problem which is stated below. When we talk about ${NO_3}^-$ we draw its structure as following But the thing which I dont understand is ...
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71 views

Bond dissociation energy among halogens [duplicate]

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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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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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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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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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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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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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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138 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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Can a s orbital overlap with any p orbital to form a sigma bond?

In internet resources, only $p_z$ orbitals are shown to overlap with $s$ orbitals to form sigma bond. But my teacher says that according to Valence Bond Theory, $s$ orbital overlaps with all three $...
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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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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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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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2answers
735 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 ...
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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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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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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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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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635 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 ...
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378 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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350 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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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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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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311 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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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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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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975 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 ...
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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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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. ...
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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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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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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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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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893 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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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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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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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 ...
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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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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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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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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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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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731 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 ...