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Questions tagged [notation]

A system of written symbols used to represent qualities or quantities, elements or molecules, or formulas in general. Usually a notation follows a convention or a guideline, often published by IUPAC-IUPAP. This tag should be used for questions regarding the proper use of a notation or misleading or ...

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Question about reaction notation (commas, numbers, and dashes)

I'm learning Organic Chemistry and in my university course we're using commas, numbers, and dashes in the reactions. My question is: What is the difference between these 3 forms of notation? $$\ce{-...
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Why do we use Δ to mean heating?

To express heating, we usually use $\Delta$ over reaction arrows like \begin{align} \ce{CaCO3 ->[\Delta] CaO +O2}. \end{align} Why do we use $\Delta$ to mean heating during chemical reactions? I ...
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1answer
40 views

Formulae distinguished only by case [closed]

A recent question (on $\ce{CI}$ v $\ce{Cl}$) reminded of this question: are there any real (as opposed to contrived) formulae which would be the same if case was ignored? One certain example is $\ce{...
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Molecular orbitals symmetry - states notation

I'm reading some papers and I'm repeatedly seeing the following notation of system states: Could you, please, explain to me the meaning of it? E.g. the state $B^2 \Sigma_u^+$ - I'm aware, that $\...
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What is LSD-1, …, LSD-24, LSD-26, …?

LSD (lysergic acid diethylamide) was formerly often referred to as ‘LSD-25’. If it really is a (Albert Hofmann / Sandoz)'s code name (and not a combination of ‘LSD’ and usual LSD (Delysid) dosage ...
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Referring to numbered atom (e.g. C-1 vs C1)

Is there a recommended style how to designate an atom by its number according to the structure numbering (given by nomenclature, or any other one in the text context)? The are (at least) two ...
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31 views

How to type condensed formulas in ChemDraw?

What I want is shown in the bubble 1, while what I keep getting every time I change the single bond to a double bond is shown in bubble 2. The H of the middle C in bubble 2 keeps shifting down when I ...
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Can the CDK represent a mixture of stereoisomers

Biovia (previously MDL) Enhanced Stereochemical Representation enabled specifying mixtures of enantomiers by annotating sterocenters with a group and one of these types: ABSOLUTE: Stereogenic ...
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differentiate between the subscript(s) and coefficient(s) that make up the chemical formula for sulfuric acid, 2H2SO4 [closed]

Im confuse on whats the question is asking. differentiate between the subscript(s) and coefficient(s) that make up the chemical formula for sulfuric acid, $\ce{2H2SO4}$.
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What does this reaction notation mean? [duplicate]

I encountered the following notation to denote a reaction, $$\ce{^{37}Cl(\nu_e,e^-) ~ ^{37}Ar}$$ What does this notation represent in terms of a reaction equation or equations? For example, does it ...
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What symbol should be used for the Michaelis constant? [closed]

I have found two different abbreviations for the Michaelis constant: $K_\mathrm M$ with capital subscript M, and $K_\mathrm m$ with a regular m. Which form is better for use in an article to be ...
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51 views

How must elemental symbols be ordered in the formula for a compound?

An online problem asked me to find the molecular formula of a certain substance given its mass composition. I found that it was $\ce{N_5P_5Cl_{10}}$. It was incorrect and told me the ordering of my ...
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Is there a difference between Ca++ and Ca(2+)?

In this EKG tutorial it says Depolarization conducts slowly through the AV node, since it is carried by slow moving $\ce{Ca++}$ ions... Is there a difference between $\ce{Ca++}$ and $\ce{Ca}^{2+}$?...
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Is there a concise notation for a solution of one substance in another?

I'm aware of phase notation of $\ce{(aq)}$ for aqueous solutions. Is there something similar for solutions of chemical X dissolved in chemical Y?
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Is it wrong to write a coefficient of 1 in a chemical equation?

Take $$\ce{2H2 + O2 -> 2H2O}$$ Is it wrong to write $$\ce{2H2 + 1O2 -> 2 H2O}$$ By wrong I mean that it is against a widely accepted guideline (those of the IUPAC?), not just "your teacher said ...
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119 views

Formating chemical equations for proteins binding in hugely complex configurations

In a previous question I asked about a simple case, I'm now trying to write equations for proteins that bind multivalently. In the simplest case proteins $A_1$ and $A_2$ can bind to up to two $L$ ...
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1answer
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Formatting a chemical equation [closed]

I recently came across this chemical equation : $$\ce{2HNO3 + Na2Co3 -> 2NaNO3 + CO2 + H2O}$$ The equation describes the reaction between Nitric Acid and Sodium Carbonate, the equation states ...
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Unknown notation relating to stoichiometry

I have never seen the highlighted symbol before. What is the name of the symbol itself, and what does it mean in this context?
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96 views

What does this three-number isotope notation mean? [duplicate]

What does the superscript $3+$ mean? $$_{21}^{45}\mathrm{Sc}^{3+}$$ I understand that $45$ is the atomic mass number and $21$ is the number of protons. Is the $3+$ to indicate that it is a particular ...
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3answers
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Typography of multi-letter variables

Chemical elements are typeset with upright font ($\ce{H2O}$ for water) while variables are typeset with an italic font ($V$ for volume). But is there a convention what to do with multi-letter ...
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2answers
700 views

What does the M in μM-Sux stand for?

I am looking at some data regarding a study around a channel-blocking agent called suxamethonium. The histograms of the open times of the channels at varying concentrations of suxamethonium are ...
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1answer
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What does an equal sign mean in chemical equations? [duplicate]

I have been doing a bit of literature review, and have come across a few equations which use an equal sign (=) instead of an arrow, for example: $$\ce{Fe^2+ + 1/2O2 = 2Fe^3+ + H2O}$$ What does the ...
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Arrows used in chemical reactions

A point was raised about arrows used in a chemical reaction. I think we can all agree that $\ce{->}$ arrow in the reaction $$\ce{A + B -> C} \tag{1}$$ means that the reaction goes in one ...
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Regarding Crystal Field Theory, where do the names eg and t2g come from?

So with Crystal Field Theory, a metal anion in an octahedral coordination complex has two sets of separately degenerate d orbitals--that is to say, the metal's dxy, dxz, and dxz orbitals are of a ...
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Notation for specific/volumetric entropy

I'm working on a problem related to entropy, and for this particular use case it's advantageous to write down properties in 'specific' units. In the case of entropy (with units Joules over Kelvin, I ...
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2answers
71 views

Atomic mass number and mass number in atomic symbol

In chemistry classes or even many different branches of chemistry textbooks, I am told that the atomic symbol $$\Large ^A_Z\ce{X}$$ includes the following notations: $A$ – "atomic mass" or "mass ...
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Platt's Notation/Nomenclature for transitions

How do you read Platt's Notation / Nomenclature? Where can I learn this? Some examples where I've seen this mentioned: In Platt's notation the transitions are designated as $\ce{A -> B}$ and $\...
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1answer
88 views

Why is a comma used to separate hydrogen gas and platinum when using cell notation?

I have come across many online articles and books where I see the following: Gaseous electrode Gases such as $\ce{H2}$ and $\ce{Cl2}$ can act as anode and as cathode by loosing electrons ans ...
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1answer
438 views

Typesetting of the retardation factor (Rf)

What should be the typesetting for the symbol of the retardation factor as used in thin-layer chromatography? These are the possibilities: Rf - only f in italics Rf - both R and f in italics Rf - ...
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1answer
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Should the mean energy be written in angular brackets or with an overline?

How would you write mean energy? I came up with two different ways: $\displaystyle\langle G_{\textrm{f}}^\circ(j) \rangle$ with the MathJax code ...
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245 views

What is the correct way to notate conformation preferences of polysaccharides?

In some webpages (1 or 2) are found the way to notate the conformational preferences of monosaccharides such as furanose and pyranose. But, it lacks to give a brief description on how to do it with ...
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Oxide content description

From time to time, I come by to see what people do with my mhchem package. Here, I came across a notation that I did not know yet: $\ce{K2O-nSiO2-xH2O}$ and $\ce{K2O - 3.2SiO2 - 2.7H2O}$ What is this?...
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559 views

Does adding prefixes to SI units make them no longer SI units?

Our chemistry professor said that "mg for mass, g/m3 for density, ms for time are all SI units". I want to make sure now, even if we added a prefix to the unit, will it still be an SI unit?
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When writing out synthetic reaction schemes, why are some reactions combined in one arrow?

An example of what I mean is here in the synthesis of compound 13. The reaction of the first arrow describes a single reaction, whereas the second arrow to form the final compound seems to have five ...
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Formating chemical equations for proteins binding in multiple configurations

I am working on problems involving protein-protein binding, particularly ones in which two proteins may bind in two or more configurations, and where some of the resultant structures may also bind ...
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1answer
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What are SN1' and SN2' reactions?

I went through the problems on the pictures: The answer of the problem 119 is $\mathrm{S_N1'}$, and that of 120 is $\mathrm{S_N2'}$. I actually can't figure out what $\mathrm{S_N1'}$ ($\mathrm{S_N1}$...
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How to accurately abbreviate solvents?

IUPAC Red Book in section IR-4.4.4 Ligand abbreviations [1, p. 63] states the following: N.B. Abbreviations for solvents that behave as ligands should also be in lower case letters [e.g. dmso for ...
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How should a triple bond be depicted in skeletal structures?

Draw the skeletal structure for the following compound: $$\ce{HOCH2CH2OCH2C#CCH2CH(CH3)2}$$ I can't figure this out. I can draw it up until the triple bond. My professor marked off because the ...
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700 views

What do the brackets mean in this inline structure representation?

Based on the way the molecular formula is written — $\ce{Br(CH2)4Br}$ — I'm assuming this means that there are $4\ \ce{-CH2}$ groups attached to $\ce{Br}$. Am I correct? I've always thought that $\ce{...
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1answer
252 views

Physical state of the carbon denoted with “gr”

I would like to know what does a gr mean when used to represent the physical state of the carbon, for example, in the synthesis of the glucose $$\ce{6C_{(gr)} + 6H2_{(g)} + 3O2_{(g)}-> C6H12O6_{(\...
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2answers
467 views

Proper common notation for a ligand

I've observed several notations for the ligand in the literature in general, say, for the typical complexes like $\ce{MX_n}$ ($\ce{M}$ - metal) where ligand $\ce{X}$ is denoted as (according to my ...
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What are the essential arrows for entering chemical equations in text?

I'm the author of a custom chemistry keyboard on iOS. I am looking at improving the selection of Unicode arrows I can provide. When the device is a phone in portrait mode, I don't have a lot of extra ...
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1answer
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How to wedge d/hash notation a molecule?

This is probably trivia for many of you (I already feel the pressure by even posting this question). Yet funny enough, most of the time the materials I have come across show the wedge-d/hash notation. ...
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396 views

State symbol for electron

Is it correct to write a state symbol of "g" or "l" for an electron? In the textbook I am currently reading, the state symbol "g" was used for the electron when it described the electron gain by a ...
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What does the Pi stand for in the reaction for biological nitrogen fixation?

In the reaction for biological nitrogen fixation, what does the Pi stand for in the products? $$\ce{N2 + 8H + 8e- + 16 ATP -> 2NH3 + H2 + 16ADP + 16 P_{i}}$$
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Multiple “/” in catalysts

What does it mean if a catalyst has multiple "/" symbols, such as $\ce{Mn/Fe/Al2O3}$? Does it mean either $\ce{Mn}$ or $\ce{Fe}$, or does it mean both are supported on $\ce{Al2O3}$?
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Why is absorbance the negative logarithm of transmittance?

What is the physical significance of absorbance? Is it not possible to directly decipher the amount of radiant energy absorbed by the sample from transmittance? Why is that negative log of ...
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1answer
109 views

Why is the notation for reactions not explicit? [closed]

I hope that the title of the question is not completely wrong or misleading, however I couldn't think up of a better one. I have a follow up question to this one. If we look at the following reaction,...
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Covalent Compounds In Written Form [duplicate]

How do you determine which non-metal is written first in a covalent compound? This has been a confusion for me for quite some time.
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474 views

Hyphenation of chemical names

When a word has to be split broken into multiple lines, it is almost always hyphenated. Chemical names can be considered words, or at least they consist of words. So the hyphenation should apply to ...