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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7
votes
3answers
9k views

How to determine bond length and angle in a conjugated pi-system (polymethine)?

I have a polymethine molecule with let's say 9 $\ce{C}$ atoms. $\ce{H-CH=CH-CH=CH-CH=CH-CH=CH-CH3}$ How can I calculate the length of the whole molecule? I need this number to compute the ...
22
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2answers
7k 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? ...
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 ...
2
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1answer
68 views

Why do many hypervalant chemicals have non-constant bond angles?

According to the VSEPR model, when a molecule in formed in the shape of $\ce{AB_{x}}$, like $\ce{IF7}$, $\ce{SCl6}$, and $\ce{PCl5}$, its structure is found by reducing the repulsions between ...
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, ...
2
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0answers
29 views

What is the mean curvature of nitrates and nitrites?

I am reading the book Soft Matter Physics - Synthetic and Biological Self-Assembling Materials from Hamley and particularly page 201. I started to think how this packing occurs in case of molecules ...
3
votes
1answer
4k views

Why does Fe(CO)₄ adopt a tetrahedral, as opposed to square planar, geometry?

Why does $\ce{Fe(CO)4}$ adopt a tetrahedral, as opposed to square planar, geometry? Here's my analysis: Factors for square planar: coordination: 4 $\ce{Fe(0)}$: d8 $\ce{CO}$: strong field ligand (...
7
votes
2answers
10k views

What is the molecular geometry of NHF₂?

I had to draw the molecular shape for $\ce{NHF2}$ as a Trigonal Planar like this But when I check to make sure it was right, I came across a source saying NHF2-difluoroammonia--tetrahedral, ...
10
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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?
1
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1answer
884 views

Build the geometric structure of SnBr2

What is Sn valence in this case? Because it depends on it if it will be linear or tetragonal.I'm talking about a molecule.
2
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3answers
2k views

What is the geometrical structure of OF₂?

Is it linear, angular, triangular or tetragonal? Well, since $\ce{O}$ has 2 electron matches of his own, I think it's tetragonal, but in wikipedia it is angular... Why? What about $\ce{CS2}$, is it ...
7
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2answers
992 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
40k 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. ...
3
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1answer
8k views

Why does the phosphorus trifluoride molecule have dipole moment?

My book says that from drawing the Lewis structure for the molecule below, you can conclude that it has dipole moment. Can someone please explain why? I understand that the dipole moment expresses ...
12
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7answers
17k views

Does NaOH react with K to form NaOK or KOH?

I realized that the $\ce{-OH}$ group when it reacts with some metal like $\ce{Na}$ or $\ce{K}$ will replace the $\ce{H}$ element to form $\ce{-OK}$ or $\ce{-ONa}$: \begin{align} \ce{H2O + Na &...
3
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1answer
1k views

Why is aluminium carbide bent?

The geometry of aluminium carbide is attached. Why isn't it completely linear (in accordance to VSEPR), but bent on the Al atoms?
2
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1answer
4k views

What is the oxidation state of nitrogen in nitrate ion and what is its structure? [duplicate]

What's the oxidation state of nitrogen in $\ce{NO3-}$ ion. Simple calculation depicts that it's $+5$. But second period elements never show variable oxidation states. And it's structure is so ...
2
votes
1answer
780 views

What is the geometric formula of CaI2 and AlCl3

Well, I think $\ce{CaI2}$ is the same as $\ce{BeH2}$ and $\ce{AlCl3}$ the same as $\ce{NH3}$, but I'm not sure since $\ce{I}$ and $\ce{Cl}$ have their own pair electrons and I don't know if this ...
3
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1answer
3k views

Electron Pair Geometry in Ibuprofen (Electron Pair Geometry in Organic Compounds)

I am trying to determine the electron pair geometry (and molecular geometry) of some atoms in ibuprofen. The first one I am trying to do is the double bonded oxygen. Ibuprofen is pictured below: I ...
3
votes
2answers
5k views

What are the bond angles in cyclohexane?

In the chair conformation of cyclohexane, what are the angles of the triangles defined by: a carbon atom, an axial hydrogen bonded to it, and the midpoint of a vicinal C-C bond ? a carbon atom, an ...
6
votes
2answers
5k views

Wade's rules for Zintl ions

How do you apply Wade's rules to Zintl polyhedral cluster anions ? For example, I believe $[\ce{Bi_3}]^{3-}$ is a triangle. My approach to justify would be: 5 electrons per each Bi atom 3 electrons ...
2
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1answer
133 views

How do I convert zwitterions to neutral form in Avogadro?

I'd like to be able to convert zwitterions to neutral form in Avogadro if possible. How do I do this?
3
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2answers
13k views

Why does dimethyl ether have a bond angle bigger than 109.5 degrees?

Why does dimethyl ether have a bond angle bigger than 109.5 degrees, in contradiction with VSEPR theory?
2
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1answer
1k views

How is bismuth(III) able to form 3 bonds with hydroxide molecules in bismuth(III) hydroxide?

Bismuth(III), if I am not mistaken, has only two valence electrons in the 6s orbital. However it is able to form 3 bonds with hydroxide. This goes against my intuition. How is it able to form 3 bonds ...
9
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2answers
14k views

How can the hydrogen bonds in solid HF be best represented?

The hydrogen bonds in solid HF can be best represented as: The correct answer is supposed to be (c), but I don't understand why this is so. Does the strength of hydrogen bonding depend on the $\...
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
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°.
13
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1answer
11k 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 ...
0
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1answer
1k views

How to draw glucose using a Fischer projection?

I asked how to draw glucose as a Fischer projection from its given chair conformation but all I got was an unsatisfactory ad hoc explanation involving rotation of my neck muscles to somehow see where ...
63
votes
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 ...
2
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6answers
2k views

Colour of Nickel thiocyanate

What is the colour of $\ce{C2N2NiS2}$ (Nickel thiocyanate)? In most of the web sites it only molecular weight,formula and other specifications but its colour is missing every where.
-2
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1answer
631 views

Dipoles and determining molecular (a)symmetry [closed]

What is a dipole? Also, how do you know if a molecule is symmetrical or asymmetrical? For example, are the following symmetrical or asymmetrical? Can you tell just from the molecular formula? Which ...
0
votes
1answer
8k views

Describe the bonding in a tribromide anion, what is its structure?

I'm thinking it will be linear with a negative charge on the middle bromine. Someone told me it is trigonal bipyramidal geometry with 3 lone pairs around the central bromine and the two other bromines ...
4
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0answers
60 views

Interpreting the MOs of a molecule [closed]

I've been looking at the MO:s of different molecules in Avogadro, fascinated by their magnificent geometries. But how is one supposed to interpret them, so as to understand their reactivity? What are ...
4
votes
1answer
962 views

How to determine the packing geometry of compounds with contradicting coordination number and radius-ratio values?

Determine the packing geometry of the following compounds by using the radius ratio rules. For your convenience assume a coordination number of six for both cation and anion. Be specific in the your ...
12
votes
1answer
692 views

Why is disilyne bent?

Why is disilyne $\ce{Si2H2}$ bent when the steric number of silicon is 2?
47
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5answers
74k 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?
3
votes
1answer
2k views

Difference between torsion, out of plane, coplanar and perpendicular bends?

In Infrared spectroscopy, stretches are easily understandable. But, how do I visualize (or conceptually understand) the difference between dihedral (torsions), out of plane bends, coplanar bends, and ...
1
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0answers
92 views

Invariants in chemistry used for model selection

What invariants related to geometrical structures that describe molecular geometry are used in chemistry? Explanation: Here, Electronic model with highest prediction rate…, one can learn about ...
3
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1answer
370 views

IBrF2 - van der Waals repulsions - and number of unique bond angles

I understand that the molecule $\ce{IBrF2}$ is T-shaped, with three ligand atoms and two non-bonding pairs. However, how many unique bond angles can this molecule exhibit? My professor argues for ...
11
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2answers
17k views

If salt crystals make a cube shape, what is this 'X' marking?

I am an amateur, with very little professional chemistry knowledge. I was doing a demonstration / experiment with my 6 year old child. We took very warm normal tap water, and dissolved into it a ...
1
vote
2answers
296 views

Determining covalent bond strengths without hybridisation

Assuming pure $\ce{2s}$ and $\ce{2p}$ orbitals of carbon are used in forming $\ce{CH4}$ molecule, which of the following statements is false? (single choice question) Three $\ce{C-H}$ bonds ...
12
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1answer
645 views

How does the pyramidalization effect the bonding angles in a distorted octahedral environment?

This is a follow up on "Generally Octahedral - Meaning?". Since Dissenter asked in the comments to my answer: I'm not sure why the $\ce{F_{eq}-S-F'_{eq}}$ bond angles would be compressed, even if ...
9
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2answers
1k views

“Generally Octahedral” - Meaning?

What does this question mean by generally octahedral? Can this molecule adopt other shapes? Also I have my suspicions about the Br-S-F bond angle being a perfect 180 degrees. Wouldn't vdW repulsions ...
9
votes
4answers
763 views

What free software exists to view molecule pictures within a file explorer?

I am testing my small api library that generates lots of chemical files such as MOL and SDF. I was wondering if there is a software that can show me the pictures of chemical structures inside each ...
2
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2answers
2k views

Dipole moment of symmetrical molecules

While studying dipole moment in organic chemistry, I got stuck at a particular statement written in the book : Symmetrical molecules without lone pairs of electrons will have $\mu = 0.$ The main ...
2
votes
1answer
253 views

Nitrogen lone pair electrons on 2-acetyl-1-pyrroline

Please consider 2-acetyl-1-pyrroline: http://en.wikipedia.org/wiki/2-Acetyl-1-pyrroline What is the molecular geometry of the nitrogen lone pair? Is the lone pair oriented in-plane with the ring? ...
4
votes
1answer
5k views

Mistake in finding bond angles in VSEPR theory

Find the bond angles as indicated, in the compounds given below, according to VSEPR theory- I got: $109.5^\circ$(6),$109.5^\circ$(7),$109.5^\circ$(8) for the compound (d). But the given answer says ...
7
votes
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, ...
4
votes
1answer
7k views

Constitutional isomers of cis-1,2-dibromocyclopentane

The following is a problem from 'Fundamentals of Organic Chemistry' by McMurry- Draw two constitutional isomers of cis-1,2-dibromocyclopentane. Constitutional isomers must have different ...