Stack Exchange Network

Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange
This site is currently in read-only mode; we'll return with full functionality soon. Follow @StackStatus or visit our status blog for more info.

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 [tag:nomenclature] or [tag:terminology].

5
votes
1answer
55 views

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?
15
votes
1answer
2k views

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 ...
5
votes
1answer
152 views

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:...
4
votes
1answer
86 views

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?
2
votes
1answer
51 views

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 ...
8
votes
1answer
282 views

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 ...
1
vote
2answers
56 views

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 ...
0
votes
3answers
128 views

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 ...
3
votes
1answer
180 views

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 ...
0
votes
1answer
21 views

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 ...
0
votes
1answer
51 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?
5
votes
0answers
45 views

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), ...
10
votes
1answer
608 views

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 ...
4
votes
2answers
143 views

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 ...
1
vote
2answers
82 views

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....
0
votes
1answer
72 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?
1
vote
0answers
30 views

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 ...
4
votes
2answers
638 views

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 ...
2
votes
1answer
64 views

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 ...
3
votes
1answer
65 views

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 ...
3
votes
1answer
41 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{...
3
votes
1answer
62 views

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 $\...
1
vote
0answers
135 views

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 ...
3
votes
1answer
25 views

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 ...
-1
votes
1answer
104 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 ...
-3
votes
1answer
225 views

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, $\ce{2H2SO4}$.
-1
votes
1answer
64 views

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 ...
2
votes
1answer
53 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 ...
1
vote
2answers
875 views

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 $\ce{Ca}^{2+}$?...
3
votes
0answers
17 views

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?
4
votes
1answer
115 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 ...
1
vote
1answer
206 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 $L$ ...
-5
votes
1answer
113 views

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 ...
9
votes
3answers
1k views

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?
0
votes
1answer
98 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 ...
14
votes
3answers
722 views

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 ...
3
votes
2answers
884 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 ...
1
vote
1answer
2k 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 ...
17
votes
2answers
2k views

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 ...
2
votes
1answer
66 views

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 ...
0
votes
2answers
103 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 ...
5
votes
0answers
247 views

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 $\...
3
votes
1answer
97 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 ...
11
votes
1answer
469 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 - ...
10
votes
1answer
94 views

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 ...
9
votes
1answer
269 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 ...
8
votes
0answers
66 views

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?...
6
votes
1answer
574 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?
5
votes
1answer
91 views

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 ...
3
votes
0answers
55 views

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 ...