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46 votes
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Are the lone pairs in water equivalent?

Water, as simple as it might appear, has quite a few extraordinary things to offer. Most does not seem to be as it appears. Before diving deeper, a few cautionary words about hybridisation. ...
Martin - マーチン's user avatar
19 votes
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What is hybridisation of XeF6 in solid state?

Forget about applying hybridization outside the second row, especially in 'hypervalent' compounds. I know, that it is common to use and sometimes works, but it is incorrect. The $\ce{XeF6}$ molecule ...
permeakra's user avatar
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19 votes
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Why are the two CH2 groups in allene perpendicular to each other?

No, VSEPR theory does not allow for a coplanar arrangement. Let us consider allene and its orbitals: Source. Green indicates $\mathrm{p}$ orbitals; blue $\mathrm{sp^2}$; and red $\mathrm{s}$. ...
ringo's user avatar
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14 votes
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What is a stereochemically active or inactive s orbital?

Generally, these terms are used to refer to lone pairs rather than s-orbitals. In the context of VSEPR theory, lone pairs usually affect molecular geometry. For example $\ce{NH3}$ adopts a trigonal ...
orthocresol's user avatar
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13 votes

When would a R-O-R bond be linear?

Oxygen can be bonded with 180° bond angles in perovskite structures, such as silicate minerals formed deep in Earth's mantle (the perovskite form of calcium silicate has been identified at Earth's ...
Oscar Lanzi's user avatar
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11 votes
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What is the Si–N–C bond angle in silyl isothiocyanate?

The answer that you are supposed to give is presumably something along the lines of "dπ–pπ" bonding between silicon and nitrogen. This essentially means that the lone pair of nitrogen is involved with ...
orthocresol's user avatar
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11 votes
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Determine the geometry of each nitrogen atom in formamidinium ion

The hybridisation of any atom is determined by the total count of its sigma bonds and localised lone pairs. This is because, while localised lone pairs occupy hybrid orbitals (as in ammonia), ...
Gaurang Tandon's user avatar
10 votes
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Are carbocations necessarily sp2 hybridized and trigonal planar?

I actually have a (or many) big issue(s) with the quote: The central C-atom is in an sp2 hybridized state, for which the carbocations have planar geometry. The p$z$-AO remains empty. The authors ...
Martin - マーチン's user avatar
10 votes
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The real structure of difluoro(dioxo)xenon (XeO2F2)

Xenon is a noble gas and thus does not need to form any bonds to complete its octet. When such a bond is formed, this is known as a hypercoordinate structure: it contains more bonding partners than ...
Jan's user avatar
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10 votes
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AB5E type molecule

Why? Because there is no other choice. Starting from the AB6 octahedral configuration, all six vertices of the octahedron are symmetric, so it doesn't matter whichever one you “choose” to replace by ...
F'x's user avatar
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9 votes

Are the lone pairs in water equivalent?

You can check out the calculated molecular orbitals of water on Professor Zipse’s (LMU Munich) page. The surrounding ‘text’ in German need not interest you, just click on ...
Jan's user avatar
  • 68.1k
9 votes

Why does NF3 have a smaller bond angle than NH3?

This can be argued on the basis of Bent's rule; concisely stated Atomic s character concentrates in orbitals directed toward electropositive substituents What follows below is a crude explanation. ...
getafix's user avatar
  • 8,475
9 votes

What is the CNC bond angle in methyl isocyanate?

This is not a good exercise question, because none of the options is actually correct. It basically asks you to blindly apply a model which cannot yield the correct result. Before continuing any ...
Martin - マーチン's user avatar
9 votes

Which molecule has maximum bond angle amongst BF₃, BCl₃ and BBr₃?

With VSEPR theory you can predict the structures of $\ce{BX3}$. Since boron only has three valence electrons, all of which are used for σ-bonding to the halogen atoms, they arrange in a trigonal ...
Martin - マーチン's user avatar
9 votes
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Comparing bond angles in carbonyl dichloride and carbonyl dibromide

The reasoning you utilized for comparing the bond angles of $\ce{NH3}$, $\ce{NF3}$, and $\ce{NCl3}$, while sensible, is simplistic and works best only for a few cases where weighing the factors of ...
Yusuf Hasan's user avatar
  • 3,196
8 votes
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Bond angles of dichlorine and dibromine monoxides

$\ce{F2O}$ Phase Method ∠F−O−F Reference solid (−223.8 °C) powder x-ray diffraction 98.0(1.5)° [1], ICSD-430183 gas microwave spectroscopy 103.07(5)° [2] $\ce{Cl2O}$ Phase Method ∠Cl−O−Cl ...
andselisk's user avatar
  • 37.7k
8 votes

Are carbocations necessarily sp2 hybridized and trigonal planar?

That notion is far from true. There are many examples of carbocations where, through the use of delocalized bonds, carbon can be bonded to five or more atoms. See, for example, https://en.m....
Oscar Lanzi's user avatar
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8 votes

Valence Bond theory, VSEPR theory and predicting the shapes of the molecules

VSEPR theory is a purely observational model, based on empirical knowledge. Many of the "rules" were added to fit the theory to what has been observed. It has quite a lot limitations and may ...
Martin - マーチン's user avatar
8 votes
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VSEPR theory, chemical bond and quantum mechanics

VSEPR is a simple and generalised approach based (mainly) on empirical observation. It is a great theory in predicting, in a first order approximation, the geometrical shape of molecules. That is a ...
Martin - マーチン's user avatar
8 votes
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Comparison of C-Cl bond length in CH3Cl and CF3Cl

The paragraph you cite does not define Bent's rule (see What is Bent's rule?, Utility of Bent's Rule - What can Bent's rule explain that other qualitative considerations cannot?). If you compare $\...
Martin - マーチン's user avatar
8 votes

Why is the molecular structure of water bent?

I mean, there is a time and place for VSEPR, and this is probably as good a time as any, because all beginning chemistry students go through it. The actual model has already been explained multiple ...
orthocresol's user avatar
  • 71.2k
8 votes

What is the CNC bond angle in methyl isothiocyanate?

I have just answered What is the CNC bond angle in methyl isocyanate? Pretty much everything written there also applies to methyl isothiocyanate, just a bit more extreme. Here is the structure ...
Martin - マーチン's user avatar
8 votes
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Possible structure if a compound like AB4 is polar?

Given all $\ce{B}$ are equivalent in terms of AXE notation, for $\ce{AB4}$ the following coordination environments are possible [1, p. 177]: square-planar $(D_\mathrm{4h},$ SP-4); square-pyramidal $(...
andselisk's user avatar
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7 votes
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Why does NF3 have a smaller bond angle than NH3?

The bond angle difference between $\ce{NH3}$ and $\ce{NF3}$ is not easily explained — but that is primarily because ammonia’s bond angles already violate the simple theories that work so well for ...
Jan's user avatar
  • 68.1k
7 votes
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What is the explanation of the structure of H2XeO4?

When I think about such structure, I draw all valence electrons around the atoms and connect them somehow reasonably. There are two ways to connect the hydrogens to xenon. Either directly bonded as H-...
pH13 - Yet another Philipp's user avatar
7 votes

When would a R-O-R bond be linear?

No, bond angles of virtually any $\ce{R-O-R}$ bond will differ from $180^\circ$, so there are no common linear oxygen configurations. Steric hindrance can cause a severe deviation from the ideal ...
Snijderfrey's user avatar
6 votes

Bond angles of dichlorine and dibromine monoxides

I think steric effects may play a role in that chlorine atoms are smaller than bromine atoms. The bromine atomic radius is about 0.15 Å larger than the chlorine atomic radius. The larger bond angle ...
XBB's user avatar
  • 73
6 votes

Why does NF3 have a smaller bond angle than NH3?

When you're comparing bond angles between $\mathrm{NH_{3}}$ and $\mathrm{NF_{3}}$, you'd want to take the electronegativities the of hydrogen and fluorine into consideration. Fluorine hits a 3.98 on ...
paracetamol's user avatar
  • 18.7k
6 votes
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Is orbital hybridisation real?

Orbital hybridisation is, like most other topics bordering quantum mechanics, just a model of reality (in fact, I would go as far as to say like all topics ever thought of, but lets not get too ...
Stian's user avatar
  • 2,795
6 votes
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VSEPR theory and hybridization in determining the shape of a molecule

The VSEPR theory can indeed be used to predict geometry a priori. You would count the number of substituents around a central atom, counting any lone pairs as substituents also, and then find an ...
Jan's user avatar
  • 68.1k

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