Questions tagged [molecular-structure]

This tag should be applied to questions that deal with the particular arrangement of atoms in a molecule, the so-called molecular structure or geometry.

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64
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1answer
9k 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 ...
48
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5answers
78k views

Why does bond angle decrease in the order H2O, H2S, H2Se?

I know that bond angle decreases in the order $\ce{H2O}$, $\ce{H2S}$ and $\ce{H2Se}$. I wish to know the reason for this. I think this is because of the lone pair repulsion but how?
21
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3answers
7k views

Why is the inversion barrier larger in PH3 than it is in NH3?

The inversion barrier in $\ce{NH3}$ is approximately $5~\mathrm{kcal~mol^{-1}}$ and that of $\ce{PH3}$ is $35~\mathrm{kcal~mol^{-1}}$. This has well-known stereochemical consequences in that amines ...
25
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3answers
179k views

How does one tell if a specific molecule is acidic or basic?

Let's take the $\ce{KOH}$ molecule into account. I know it is a base from literature, but how would one go about determining if a molecule is acidic or basic simply based on the structure of the ...
14
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2answers
23k views

Bond angles for the hydrides

I noticed the fact that all the hydrides of the elements belonging to group IV has bond angle 109.5° while in group V it varies from 107.3° for $\ce{NH3}$ to 91.3° for $\ce{SbH3}$. Similarly we see in ...
34
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3answers
6k views

Has anyone even taken a picture of a molecule to confirm the geometry predicted by theory?

Have the geometries of molecules been proven, or are we operating strictly on mathematical theory? To put it over-simplistically: has anyone ever taken a picture of a molecule to compare against their ...
23
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2answers
8k views

PBP vs TBP geometry?

Why are the axial bond lengths greater than those of the equatorial bonds in a trigonal bi-pyramid (TBP) geometry molecule; but the opposite is true for pentagonal bi-pyramid (PBP) geometry molecules? ...
25
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1answer
831 views

Do vinyl cations adopt a classical or non-classical structure?

Whilst reading this question today, I remembered something that I had seen previously here. In the second linked question, @Martin provided a reference to suggest that vinyl cations actually adopt a ...
7
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1answer
158 views

Are all stable Xenes (graphene-like 2D honeycomb sheets) buckled?

background: Per this abstract Silicene, germanene and stanene are part of a monoelemental class of two-dimensional (2D) crystals termed 2D-Xenes (X = Si, Ge, Sn and so on) which, together with ...
31
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1answer
4k views

What is the molecular structure of xenon hexafluoride?

Xenon hexafluoride, $\ce{XeF6}$, can be obtained by reaction of xenon with excess fluorine gas. What is the gas-phase structure of the molecule? What experimental evidence is there to support it, ...
8
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1answer
36k 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 ...
4
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1answer
15k views

Structure of xenon hexafluoride

The central atom has a hybridization of $\mathrm{sp^3d^3}$. Thus, its structure should be pentagonal bipyramidal. Why is it not that but a distorted octahedron?
14
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1answer
8k views

What is a stereochemically active or inactive s orbital?

In Concise Inorganic Chemistry by JD Lee (4th edition; adapted by Sudarshan Guha), page 73 under the section 3.6 (VSEPR Theory chapter Chemical Bonding): ...according to this theory, the position of ...
26
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2answers
34k views

Why is water a dipole?

Water ($\ce{H2O}$) is a dipole. The reason why is simply because it is not symmetrical, there are more electrons on the oxygen side than on the hydrogen side, and the electronegativity of oxygen. But ...
23
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3answers
5k views

What is the geometry of an alkyl radical?

I encountered this question which asks how many possible radicals are formed when $\ce{CH3CH2C(CH3)3}$ is monosubstituted by $\ce{Br2}$. The answer given is 3 while I think it should be 4, reasoning ...
7
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3answers
24k views

Why the bond angle of PH3 is lesser that that of PF3?

We can explain why the bond angle of $\ce{NF3}$ (102°29') is lesser than $\ce{NH3}$ (107°48') by the VSEPR theory, since lone pair lone pair repulsion is greater than lone pair bond pair repulsion. ...
6
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2answers
2k views

Estimation of the bond angle of water

We know from experimental data that $\ce{H-O-H}$ bond angle in water is approximately 104.5 degrees. If its two lone pairs were bonds (which is unfortunately impossible) also $\ce{O-H}$ bonds and a ...
7
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2answers
1k views

How does VSEPR theory explain the formation of different bond angles in PCl₅?

We know, that in the exited state, electrons of Phosphorus could go to higher states and form $\ce{dsp^3}$ hybridization. Therefore it will create five equal energy states of electrons. But my ...
7
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1answer
41k views

How to know it when I see a covalent network?

This is a well-known (better said: well-discussed) question in the internet. When you look for answers for popular questions, you usually see them with a variable degree of reliability and complexity. ...
7
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3answers
11k views

Shape and polarity of the iodate ion

I am trying to figure out the shape of the iodate ion or $\ce{IO3^-}$. No matter how many times I draw it, I keep getting iodine in the centre, and 3 oxygen atoms surrounding it, 2 with single bonds, ...
12
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1answer
8k views

Why are the two CH2 groups in allene perpendicular to each other?

Allene, $\ce{H2C=C=CH2}$, has two $\ce{=CH2}$ groups perpendicular to each other. This is the same as hydrogen peroxide's $\ce{H}$ atoms. Is there any reason why they adopt the perpendicular ...
15
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1answer
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Basicity Alteration Due To Ortho Effect In Methoxy Aniline System

I wanted to ask something more in reference to this question. Suppose instead of toluidine, 2-methoxyaniline and 3-methoxyaniline are present. Now, why is 2-methoxyaniline more basic than 3-...
11
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4answers
1k views

Does benzene structure stand for a single resonance form or the whole molecule?

It is known that benzene has two main resonance forms Often we still draw benzene molecule as one of them My question is, actually when we draw the lower figure, do we refer to the whole benzene ...
1
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1answer
2k views

Determine the bond angle in a compound [closed]

How can we find the bond angle between 3 atoms in a compound? Please specify an equation which can be used for all compounds.
7
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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, ...
7
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1answer
333 views

Geometries of methyl and silyl radicals

The $\ce{.CH3}$ radical is planar but the $\ce{.SiH3}$ radical is a trigonal pyramid. Why are they different? After all, $\ce{C}$ and $\ce{Si}$ are in the same group.
-1
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1answer
114 views
18
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3answers
43k views

Bond order for carbonate ion for resonance

I saw in a textbook that for carbonate ion, there are 3 resonance forms and the bond order is 1 and 1/3. So in general, how should we calculate the bond order for resonance structures? Is there any ...
14
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3answers
2k views

How do I make 3d molecular graphics similar to those shown on Wikipedia?

I want to make 3d molecular graphics similar to those found on Wikipedia. In the page for benzene, you can see the structure looks like this: However, if I go to the interactive image as shown in ...
16
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2answers
682 views

What are the important implications to the field of chemistry, if any, of the recently confirmed hexavalent carbon species?

I’m struggling to understanding the true nature and implications of recent confirmations of the existence of stable species containing carbon atoms bound six (in another case 5) other carbon atoms. Is ...
13
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1answer
12k views

How do electronegativity and lone pairs affect bond angles?

How do bond angles vary in molecules with a lone pair and central atom of different electronegativity, but in the same period so that electronegativity matters more than orbital size? Let's assume ...
14
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1answer
1k views

Bonding in Square Antiprismatic Compounds

Both $\ce{IF_8^-}$ and $\ce{XeF_8^{2-}}$ have (distorted) square antiprismatic geometries. I've been wondering how to explain the bonding in such compounds. Hypercoordinate bonding (as used to ...
7
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6answers
1k views

Free API to view 2D representation of Molecules

I'm looking for a free API that can accept a SMILE and produce the 2D structure of a molecule. I would like to include this in a web page. I have collection of SMILES and would like to have the 2D ...
12
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1answer
728 views

Why is disilyne bent?

Why is disilyne $\ce{Si2H2}$ bent when the steric number of silicon is 2?
7
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2answers
244 views

Why does a larger bond angle correspond to greater s-character?

In trialkylamines $\ce{NR3}$, the $\ce{R}$ alkyl group attached to nitrogen increases the electronegativity of the nitrogen atom. I also found in this question that this happens due to the repulsion ...
5
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2answers
524 views

What is the correct way to verify a structure's geometry, for example for benzene?

My goal is to compare a calculated bond length with experimental data. Benzene is obviously common enough to expect sufficient experimental data to be available for it on the internet. I have found ...
9
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1answer
17k views

Structure of Borax

The structure of Borax has really baffled me. Its formula is $\ce{Na2B4O7.10H2O}$ and it is formulated as $\ce{Na2[B4O5(OH)4].8H2O}$. 2 structures of Borax given on the internet are Can anybody ...
10
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1answer
3k views

Why does the fructose monomer in sucrose appear different from isolated fructose?

I understood that the representation of fructose is: But during the formation of sucrose: How did fructose, whose representation is given in the first picture, turn out to be different in the ...
10
votes
6answers
31k views

What is the Lewis structure for HClO?

In many sites, I see that they put $\ce{O}$ in the middle, but our teacher said that we should put $\ce{O}$ near the extremity. Which is the best way?
8
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3answers
12k views

Why is the H−C−H bond angle in сhloromethane larger than 109.5°?

Symmetrical tetrahedral molecules (like $\ce{CH4}$) have a bond angle of $109.5$. Those with lone pairs in place of one atom (like $\ce{NH3}$) have bond angles less than $109.5$. The standard ...
7
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1answer
5k views

Why is the methyl radical planar?

Why is the methyl radical planar? The VSEPR theory would predict an angle between 120° and 109.5°, while it is actually 120°.
10
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3answers
357 views

Have "molecular clusters" for azeotropes been identified?

A different question about azeotropes got me thinking about this point again. Azeotropes have a very specific composition so it seems that the azeotrope ought to have some sort of physical structure. ...
8
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3answers
3k views

HCH bond angle in cyclopropane and cyclobutane

I understand why the $\ce{CCC}$ bond angles in cyclobutane and cyclopropane are less than ideal $109.5^\circ$ due to the geometric restrictions they encounter in a cyclic structure. However, it is not ...
8
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1answer
2k views

Why is there only one bond length for sulfur hexafluoride?

In sulfur hexafluoride, there are two 3-centre 4-electron bonds, according to the book I am reading (Essential Trends in Inorganic Chemistry by D. P. M. Mingos). The other two fluorines are bonded to ...
6
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1answer
14k views

How can placing a lone pair in axial position differs from that in equatorial in number of electron domains?

I need help understanding the following statement in my book (regarding trigonal bipyramidal geometry): Placing a lone pair in an axial position would put it at 90 degree to three other electron ...
6
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1answer
371 views

Have the shapes of synthesized anthropomorphic molecules (nanoputians) been verified experimentally?

Have the shapes of synthesized anthropomorphic molecules (nanoputians) been verified experimentally? X-ray diffraction, atomic force microscopy imaging of single molecules, anything? I was tempted ...
5
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1answer
527 views

Structure of lead(II,IV) oxide

I need help sorting out the molecular structure of tri-lead tetroxide, aka lead(II,IV) oxide $\ce{Pb3O4}$. This data sheet shows this image: The Wikipedia's lead (II,IV) oxide's link to a Jmol ...
1
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3answers
23k views

Identifying the number of bonding and lone pairs without a dot and cross diagram

I've just learned how to predict the shapes of molecules in class today using VSEPR theory. I would like to ask is there anyway to find the number of bond pairs and lone pairs without drawing a dot-...
1
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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 ...
-1
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1answer
854 views

What are the structures of potassium superoxide and xenon hexafluoride? [closed]

I have 2 questions in mind: 1) What is the structure of the superoxides? More specifically, what is the structure of $\ce{KO_2}$? 2) What is the structure of and dipole moment for $\ce{XeF_6}$?