Questions tagged [molecules]

An electrically neutral entity consisting of more than one atom (n > 1). Rigorously, a molecule, in which n > 1 must correspond to a depression on the potential energy surface that is deep enough to confine at least one vibrational state. This tag should be applied to question about certain molecules or a class of them.

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48
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2answers
17k views

Why is an S-S bond stronger than an O-O bond?

I'm wondering why exactly the single bond between two sulfur atoms is stronger than that of two oxygen atoms. According to this page, an $\ce{O-O}$ bond has an enthalpy of $142~\mathrm{kJ~mol^{-1}}$, ...
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4answers
961 views

Do symmetric hydrogen bonds in neutral molecules exist?

As far as I know, there have only few truly symmetric hydrogen bonds been observed. Unquestionable is the existence of it in the bifluoride ion, $\ce{[F-H-F]-}$, see also here. There are a couple of ...
34
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3answers
1k views

Proper typography of “NOx”

I am a journal typesetter, and recently I came to a problem that I'm not sure I know to solve. The question is how to properly typeset the "NOx" abbreviation for nitrogen oxides. Which is ...
27
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1answer
1k views

Are long oxygen molecules possible?

Are large oxygen containing molecules possible? Either large rings, or chains with hydrogen atoms at the ends. Like this: $\ce{H-O-O-O-O-O-O-O-O-O-$\cdots$-O-O-O-O-O-H}$
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4answers
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Is a diamond a single molecule?

Assuming a perfect diamond with no impurities. Would this diamond considered to be a single large molecule? Browsing the interweb I found several opinions about this but did not find a clear Yes or No....
24
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1answer
2k views

Why do the atoms in molecular models have the colors they have?

Molecular models are a great tool for visualizing a molecule in three-dimensional space. These models even appear on the web (practically every chemical's Wikipedia page), and there is a very specific ...
23
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2answers
71k views

Why do different substances have different boiling points?

For example, why does for example oxygen turn into gas at a much lower temperature than water? Does it have anything to do with the molecular structure? A water molecule does have a more complex ...
20
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4answers
403 views

How to explain the concept of mol and reactions involving mol quantities

From time to time I do little pro bono lessons for second grade in math, physics, and chemistry. Recently I came across this question. In a container is $2~\mathrm{mol}$ of $\ce{SO3}$ (sulfur ...
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2answers
5k views

Which relatively simple molecules violate the octet rule?

I'm learning how to draw Lewis diagrams. Everything I've read emphasizes the octet rule. However, to the best of my knowledge, that rule only applies to elements in the first three periods. On our ...
19
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4answers
23k views

What is the difference between physical and chemical bonds?

If you characterize the chemical bonds to two categories physical and chemical bonds, how do you do it? Aren't all bonds chemical and physical? From the freedictionary.com, chemical bond: Any of ...
19
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1answer
668 views

Symmetrize nearly symmetric molecule

In the overall good paper of Beruski et. al.,[1] an algorithm of how to symmetrize an "almost symmetric" molecule by symmetrizing the distance matrix is given for the example of Methane. The ...
18
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2answers
1k views

How do the molecules know the future? How do they proceed to form “Most Stable” compound?

I'm tutoring few students for Chemistry. During the course, I many times use the phrase "Out of these possibilities this one is stable. So it is formed". I get questions like, "How do the molecules ...
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1answer
3k views

Why do methane molecules have 15 degrees of freedom?

I've just been learning a little thermal chemistry including the equipartition theorem. As part of this, my textbook discusses how to figure out the degrees of freedom for different chemicals. The ...
15
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5answers
7k views

Can fluorine act as the central atom in interhalogen compounds?

Why can't fluorine be the central atom in inter-halogen compounds? A $\ce{F-F}$ bond is weaker than a $\ce{F-X}$ bond and thus, fluorine should be happy to form inter-halogen compounds. But, why ...
15
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1answer
794 views

Are there molecules that take the shape of every platonic solid?

Methane is the simplest molecule I know of that takes the shape of a platonic solid — in this case, the tetrahedron. Wikipedia has a page on platonic hydrocarbons that includes molecules with ...
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2answers
6k views

Electron density definition of single, double, triple bonds?

I was reading this question and the answer by user EricBrown to it, and this got me thinking about covalent chemical bonds. The way I was always taught is that a single bond contains 2 paired ...
13
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2answers
7k views

How to know whether s-p mixing will happen in heteronuclear molecules?

How do I know whether s-p mixing would occur in some diatomic heteronuclear molecules like CN, CO, NO etc?
13
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1answer
3k views

Do noble gasses besides Helium form diatomic molecules at low temperatures?

I know that at extremely low temperatures (mK and lower), Helium can form diatomic molecules. Do the other noble gasses also form molecules at extremely low temperatures?
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2answers
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What causes spray cans to get cooler when shaken?

I've been searching the web for this phenomenon and surprisingly I found only one post about it. And the reply to this question about canned air begins with words: I don't know about the shaking ...
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7answers
4k views

Are there any good examples of commonly ingested molecules that contain particular toxic individual elements?

In the house on my own and an article popped up on my feed with the following statement: While the Government has insisted the chemical is safe, cadmium is recognised as a cause of lung cancer ...
12
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5answers
9k views

Is there a way to use free software to convert SMILES strings to structures?

So far I've been unsuccessful in finding an open source tool that will convert a large number (>100k) of SMILES strings to a chemical structure. Is this really only solved by commercial applications? ...
12
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2answers
26k views

How do noble gases bond with themselves?

Noble gases have full electron shells, which virtually blocks any other element from bonding with it. However, I've heard about cases where they bond to each other - for example, helium can ...
12
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1answer
3k views

Why six C atoms are usually seen in cyclic compounds?

When it gets to Carbon-based molecules, one very possible structure when there are more than six C atoms is the hexagon; though not mostly perfect, it emphasizes that six Carbon atoms tend to bond ...
12
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1answer
589 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 ...
12
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1answer
697 views

Existence of Dichlorine Pentoxide

I searched the net and a lot of books, but I was unable to find any information about dichlorine pentoxide. Does dichlorine pentoxide($\ce{Cl2O5}$) exist? If it doesn't exist, then why so? If ...
11
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4answers
16k views

Why do people still use the mole (unit) in chemistry?

I know that the mole is widely used in chemistry instead of units of mass or volume as a convenient way to express amounts of reactants or of products of chemical reactions. I'm wondering why people ...
11
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3answers
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Why do molecules having a higher relative molecular mass have stronger inter-molecular forces?

Why do molecules like alkanes with higher relative molecular mass ($M_\mathrm r$) have stronger intermolecular forces? For example, methane ($\ce{CH4}$) has a weaker intermolecular force than pentane (...
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2answers
26k views

Why are least electronegative elements usually in center of lewis structure

Many sources state that one of the primary rules for molecular structures is that the least electronegative element is in the center. However, none of them explain why this is the case. Is this ...
10
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5answers
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What actually is the Wavefunction?

I am aware that the square of the Wavefunction gives the probability density of finding an electron at a particular point in space. I have also heard that it's a complex number but since it's a ...
10
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3answers
433 views

How does a molecule search work by drawing in visual editor?

There are a lot of chemical search engines (such as ChemSpider's Structure search) that allow users to draw and search for a molecule. How does it work? Is the comparison of images used? Could you ...
10
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3answers
646 views

Explain the formation of replicators to a layman

I am reading The Selfish Gene by Richard Dawkins. I am on chapter two. He speaks of the observation of the formation of amino-acids when you simulate environmental conditions of primordial earth. ...
10
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2answers
1k views

How long do the bonds in a molecule hold under nominally stable conditions?

Disclaimer: I am not a chemist I was just drinking my Ice Age mineral water which is 'untouched since the Ice Age' and wondered if the bonds formed in each molecule have remained intact for all those ...
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2answers
2k views

How does glue work?

Simple question. How does household glue work? How does it attach to almost any other compound? Thanks.
10
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1answer
296 views

Standards for drawing chemical molecules

I'll preface this by saying I haven't had a chemistry class in 10 years and molecular structures are not my thing. But I'm submitting a revision to a journal paper where I need to include figures of ...
10
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1answer
823 views

Materials with solid volume greater than liquid volume

Water has a solid volume greater than its liquid volume. This question is in two parts. 1) Are there other materials that have solid volumes greater than liquid volumes? 2) What about the structure ...
10
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1answer
20k views

Why does SO2 have a larger bond angle than H2O, H2S, and NH3

So we have to find which of the follwing compounds has the smallest bond angle: $\ce{H2O}$, $\ce{H2S}$, $\ce{NH3}$, $\ce{SO2}$. So L $\propto \frac{1}{BA}$ where $L$ is the number of lone pairs and $...
10
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3answers
1k views

When did the atom Theory Become indisputable?

We know that the Greeks were the first scientists (or better, philosophers) to introduce the idea that matter is made up of little “chunks”, and they named these chunks “atoms”. This idea that matter ...
10
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1answer
2k views

What makes water a liquid (when it is)?

I'm curious about what the minimal conditions for some collection of water molecules to be liquid water are. What is the minimum number? What sort of bonds must hold? What other sorts of things I don'...
10
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0answers
966 views

What makes a compound a dehydrating agent?

When a carboxylic acid with low molecular weight is heated with $\ce{P2O5}$ we get the corresponding anhydride. My book says that this reaction happens with dehydrating agents such as $\ce{P2O5}$. I ...
9
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3answers
38k views

What is the difference between “molecular mass”, “average atomic mass” and “molar mass”?

I don't understand the difference between "molecular mass" and "average atomic mass". They seem like the same thing to me. Is it that average atomic mass is just the weighted average of the "weights"/...
9
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2answers
4k views

Why do single elements in a molecule have an oxidation state of zero?

For example, take $\ce{O2}$. The oxidation state of oxygen is -2, yet once its in a molecule its oxidation state becomes zero? How is this so?
9
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1answer
15k views

Why do single, double and triple bonds repel each other equal amounts?

I'm here to share with you something that totally confuses me, as I can't see the logic behind it, and my teacher doesn't know either. Let's take a set of bonds that's trigonal pyramidal, with a lone ...
8
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3answers
7k views

Law of Multiple Proportions: What is the significance of small whole numbers?

I'm new to Chemistry and in my textbook, it describes the Law of Definite Proportions (aka Proust's Law) and then goes on to describe the Law of Multiple Proportions. The example they give is carbon ...
8
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3answers
26k views

How to get the valencies of elements?

How to find the valencies of elements by using its distribution of electrons? Please explain the method in simple words. Do you have to study the valencies or is there a simple way of remembering? PS:...
8
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2answers
3k views

Is there any scenario in which the size of a molecule increases due to an increase in temperature?

Take an ice cube for example. Heat is applied in a closed container until it is vaporized completely. Will the molecule's size be larger (on average)? Is there a substance that you know of that has ...
8
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1answer
35k views

What holds atoms together? [duplicate]

I know atoms are held together by Ionic and Covalent bonds and i understand the ionically bonded atoms are held together by electrostatic forces. What about covalent bonds? How are molecules of bonded ...
8
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1answer
39k views

Molecular orbital theory & predicting the stability of a molecule?

A question in my general chemistry textbook gives me a list of formulas for molecules and ions. It then asks me to determine, using molecular orbital theory, whether or not each would exist in a ...
8
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3answers
6k views

What is difference between intramolecular redox and disproportionation redox

I can not understand difference between the intramolecular redox reaction and the Disproportionation redox reaction. Both involve the same molecule as substrate, but what is difference?
8
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1answer
660 views

What is kekulization (in RDKit)?

It's been a while since I've studied chemistry. Now, I am reading the documentation of RDKit. At a certain point, the term "kekulization" is mentioned. What is kekulization (in RDKit, if this is not a ...
8
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1answer
541 views

What does the 129Xe NMR spectrum of XeOF4 look like?

What will the $\ce{^129Xe}$ NMR spectrum of $\ce{XeOF4}$ look like? I know that its electron pair geometry is octahedral, and the molecular pair geometry is square pyramidal. I believe that the ...