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 uncommon notation in the scientific literature. Do not confuse this tag with the [nomenclature] or [terminology] tags.

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How are lowercase k and uppercase K used in general chemistry courses? [closed]

Where do lowercase k and uppercase K make appearances in general chemistry, and what do they signify?
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How are lowercase m and uppercase M used in general chemistry courses? [closed]

Where do lowercase m and uppercase M make appearances in general chemistry, and what do they signify?
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Gibbs Free Energy Notation

What's the difference between $G$, $\Delta G$, $\Delta G^\circ$, and $\Delta_\mathrm r G^\circ$? I've seen the first two used interchangably, and seen $G$ specifically referred to as change in Gibbs ...
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For a benzene shown in a skeletal structure, what does a substituent to the center of the ring mean? [duplicate]

I have seen diagrams with both the substituents attached to the benzene ring by the edges and other occasions directly to the delocalized ring. What does signify?
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Confused by notation of atomic number Z and mass number A on periodic table of elements

I'm totally confused by the different conventions and when to use what. In the Periodic Table I see $$\ce{^{6}_{12}C}$$ However, in books when talking about isotopes I see $$\ce{^{12}_{6}C}$$ I ...
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1answer
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Can a double bond extend beyond the plane and if so, how would it be drawn?

Can double and triple bonds, etc., extend beyond the plane in a Lewis structure, and if so, how are they represented? I.e., how would 1 and 2 in this image be drawn if they were doubles or triples?
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Is 1 ppb equal to 1 μg/kg?

In an article I recently submitted, a reviewer asked that I provide a concentration in μg/kg instead of ppb (parts per billion), and mentions that the later is not correct. I am not a chemist, and I ...
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1answer
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How to report a triplet of septets in NMR tabulation?

Does anyone know the proper format to report an iso-butyl group, eg. $\ce{R-CH2-C\color{red}{H}(CH3)2}$, in $\ce{^1H}$ NMR tabulation? The proton in red should be a triplet of septets, so I've written:...
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How to draw protonated benzene (horseshoe) carbocation structure with ChemDraw?

Is there a way to draw the aromatic "horseshoe" (forgot the official name) structure of a protonated benzene cation (arenium) with ChemDraw, and not the cation with double bonds?
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Using Roman Numerals to indicate a compound

I don't completely understand it's use. Here's an example I don't understand: Shortly after discussing $\ce{[CuCl4]^2-}$, an exam paper asked a question about copper(II) chloride. I understand that ...
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Does the Location of Line-Dash-Wedge Notations Matter?

In Line-Dash-Wedge notation, when illustrating that an atom or bond is directed towards or away from the viewer (solid triangle for coming forward, dotted lines for going back), does the location of ...
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Chemical formula of fluoroapatite

My textbook says the formula for fluoroapatite is $\ce{CaF2 * 3Ca3(PO4)2}$, whereas according to Wikipedia it's $\ce{Ca5(PO4)3F}$. What is the correct chemical formula of fluoroapatite and why there ...
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Conversion from a PPB value to µg/m3 of Isobutylene

I have a quite simple problem, found a lot of information about it, but I am not sure anymore if I do my calculations right. I own a sensor, which reports measurements in isobutylene units as PPB. So ...
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What does x mean in (1-x)A – xB composite materials, molar ratio, weight ratio or volume fraction?

I've been collecting data about ceramic materials and often I get to see composite materials are described as $(1-x)\ce{A} - x\ce{B}$. I am confused what this $x$ means. And I haven't seen any of the ...
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Combination of several unit symbols when finding new pressure from ideal gas law

As a car is driven, the tires heat up and the volume and the pressure change. Calculate the new pressure of a 35.0 L tire initially at 235 kPa that expands to 36.5 L when it heats up from 15.0 °C to ...
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1answer
322 views

What is the difference between ΔfH and H-H° in NIST–JANAF tables?

Can someone explain the difference between $Δ_\mathrm{f}H$ and $H-H^\circ$ in NIST–JANAF tables?
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Is there a particular name for a Hill formula or sum formula omitting hydrogen?

Often, single-crystal X-ray diffraction analysis determines the non-H atoms first, and eventually puts hydrogen atoms "as riding" on idealized positions in respect to heavier atoms (e.g., C, O, N), ...
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Why was a Plimsoll symbol chosen to indicate standard state?

Historically, the Plimsoll symbol (aka Plimsoll line) was created as hull mark that would serve as a ready indicator of whether a ship was overloaded and thus running too low in the water. It was ...
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Different formulas for copper pyrites and bauxite

In my book in the chapter on General Principles and Processes of Isolation of Elements, I found that the formula for copper pyrites was stated as $\ce{Cu2S.Fe2S3}$ at one place, $\ce{CuFeS2}$ at ...
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How do I write orders of magnitude in scientific notation when margin of error is involved?

My TA has me confused about how to use scientific notation when margin of error and orders of magnitude are involved. The number I wrote: 3.78 ± 0.02 * 10^-3 My TA told me that this means: 3.78 ± 0....
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1answer
309 views

What do D and L stand for in the Fischer-Rosanoff convention?

In R and S configuration, the R stands for rectus and the S stands for sinister. Similarly, do the D and L descriptors in the Fischer-Rosanoff convention stand for something?
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Drawing bonds and delocalised electrons in condensed formulae

The $\LaTeX$ mhchem package provides commands for drawing bonds within condensed chemical formulae. Some of them have a clear allocation to covalent bonds while others have not. Single, double, and ...
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Superscript and subscript together after the same atom

In the chemical formula of some ion compounds, there is the necessity to write the charge in the superscript and the numbers of atoms in the subscript, but together at the right of the same symbol ...
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1answer
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Depicting molecules by Natta projection

Does anyone know the meaning of these two bonds in stereochemistry? These bonds are provided by the $\mathrm{\LaTeX}$ chemfig package. The creator of the ...
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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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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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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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1answer
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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 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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1answer
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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? [closed]

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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1answer
997 views

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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1answer
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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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1answer
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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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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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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
5k views

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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1answer
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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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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 $\ce{...
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1answer
251 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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607 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 ...