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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14
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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 ...
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2answers
1k views

Approximation of electron density of a small molecule

Starting point for Quantum Theory of Atoms in Molecules (AIM) is the electron density $\rho(r)$. It could be determined experimentally (X-ray diffractions). I want to know how can we estimate them ab ...
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0answers
354 views

Polar group strong dipole effect molecular axis

There are some fundamental charactaristics of liquid crystal. One of them is that all liquid crystals are organic compounds and at one side of their long molecular foundation there exists a polar ...
3
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2answers
483 views

How different are molecule with same connectivity

Let us represent molecules by graphs (atoms are vertices and bonds are edges). Let $A$ be the adjacency matrix of the molecular graph. $A_{ij} = b$ where $b$ is either binary: 0 when atom i and j are ...
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:...
3
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1answer
761 views

Number of bonds in a Lewis Structure [duplicate]

I'm asked to find the Lewis Structure of sulfuric acid, $SO_4H^-$. After struggling for a while, I sumply looked it up. How can this be? Sulfur has 6 electrons in its valence shell, so it should ...
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1answer
66k views

How does the reaction Mg + O₂ → MgO occur? [closed]

$\ce{Mg + O2 → MgO}$ Magnesium, oxygen and magnesium oxide form the above equation. How? What do I need to learn to do this? atomic numbers/ valencies?
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 ...
4
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1answer
1k views

How long can polyethylene molecules be?

In this video, Steve Spangler says the substance he is using (a polyethylene oxide): http://www.youtube.com/watch?v=m-88M75_PCI He mentions that one molecule would go to the moon and back twice! I ...
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2answers
4k views

Tool that generates electrostatic maps of molecules?

Do you know any tools that generate electrostatic potential 2d maps of the molecules as an image?
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1answer
175 views

How to calculate weight of CO₂ in one kg of fuel

I'm trying to do homework and I have the answers to the problems but I can't read the explanation because it's illegible and I can't find how it's done in my notes. Here's the simplest example: $$\...
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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?
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1answer
2k views

How can one find products when one knows the reagents?

I'm going to use an example (I could have used a different one); On the document it is about the study of the chemical balance of an acid-basic solution. The chemists have written the chemical ...
4
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4answers
22k views

Differences between H-H-O and H-O-H

I'm not an expert. In simple words how do they differ: $\ce{H-H-O}$ and $\ce{H-O-H}$ molecules?
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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 ...
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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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0answers
747 views

Can magnesium chloride absorb water and ammonia at the same time?

Anhydrous magnesium chloride will absorb ammonia to the tune of ($\ce{Mg(NH3)6Cl2}$). Incidentally, magnesium chloride is usually a hexahydrate ($\ce{MgCl2(H2O)6}$) at STP. My question is, could ...
7
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3answers
264 views

Has the molecular diatomic oxygen trianion been observed or predicted?

Has diatomic oxygen ever been observed with a 3− charge, i.e. $\ce{O_2^{3-}}$? Have any ab intio calculations been done on this ion? Update: Just to summarize some of the answers below and add my ...
9
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1answer
16k 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 ...
2
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1answer
219 views

Find empirical formula when individual masses are known

I'd like to illustrate my question with an example: Imagine nickel reacts with fluoride and you start with $0.766\ \mathrm{g}$ of nickel, an unknown amount of fluoride and you end with $1.261\ \...
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1answer
434 views

Shape of C₂H₂ molecule

What is the shape of the $\ce{C2H2}$ molecule? The fact that is has a triple covalent bond between the 2 carbon atoms and 2 other bonding pairs between the hydrogen and carbon atoms leads me to ...
5
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1answer
233 views

Why not “Oxygate” OO4(2-)?

So many atoms can be surrounded by oxygen atoms to make anions - chromate, phosphate, etc. In particular there's Tellurate $\ce{TeO4^{-2}}$, Selenate $\ce{SeO4^{-2}}$ and Sulfate $\ce{SO4^{-2}}$ - ...
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1answer
3k views

What makes a molecule a polyatomic ion?

I checked the Wikipedia page, but it did not seem to provide a very intuitive explanation. What distinguishes a molecule such that it behaves like a polyatomic ion? I understand that it is a ...
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 ...
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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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 ...
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2answers
72k 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 ...