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].

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4
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1answer
51 views

Has anyone encountered the use of Omega to represent equilibrium?

One of my lecturers last year (a pharmacologist by training) used the symbol $\Omega ^m$ as a shorthand for equilibrium. He implied it was common practice but I've never come across it elsewhere. I ...
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0answers
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Is there a standardized way to assign a label to the symbol of a chemical element (in a published work)?

When referring to a particular atom, both in text and when using a graphical representation, several conventions are being applied. In the field of crystallography an arabic numeral either follows ...
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1answer
38 views

An exception to the IUPAC convention for italicisation (typography)

According to IUPAC, only physical quantities and variables must be italicised. Section 8 Use of Italic and Roman Fonts for Symbols in Scientific Text of ICTNS Guidelines for Drafting IUPAC Technical ...
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1answer
93 views

Confused on how to draw cis-[Ni(H2O)4(NH3)2]Cl2 [closed]

I got a question on my practice exam telling me to draw cis-diamminetetraaquanickel(II) chloride, but I'm not sure on how to place the two $\ce{Cl}$ atoms.
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1answer
73 views

Meaning of mass concentration “units” % m/v [closed]

In a saline solution that is 5.750% (m/v) potassium iodide $(\ce{KI}),$ there are: a) 5.750 mL $\ce{KI}$ per 100.0 mL $\ce{H2O}$ b) 575.0 mg $\ce{KI}$ per 10.00 mL of $\ce{KI}$ solution c) 5....
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2answers
58 views

Why do we use [H⁺] and [OH⁻] in balancing redox reactions instead of using [H₃O⁺] and [OH⁻]? [duplicate]

For what reason is it universally agreed upon that we use $$\ce{H+ + OH-}$$ ions in balancing water on either side of the reaction, but not the $$\ce{H3O+}$$ ions?
12
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2answers
636 views

“T” in subscript in formulas

Does a “T” in a formula subscript indicate all possible numbers of atoms? $\ce{FeO_T}$ is the specific one I came across (in the "bulk chemistry" table here: https://sciences.ucf.edu/class/...
10
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3answers
967 views

What does a comma signify in inorganic chemistry?

$\ce{(Ca{,}Co)CO3}$ I have never ever seen this before. What does this mean exactly?
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79 views

How to distinguish mass concentration and density?

I am writing a proof where I have to mention both with density and of a material and mass concentration (mass/volume) of a material. I am using the letter $\rho$ to represent density, and I didn't ...
9
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1answer
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What does “lit.” mean in boiling point or melting point specification?

For example, this Xanthene 99% specification from Sigma Aldrich states: \begin{array} \\\hline \text{bp} & 310-312 ~^\circ\mathrm{C~ (lit.)} \\\hline \text{mp} & 101-102 ~^\circ\mathrm{C~ (...
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1answer
239 views

How to you show a 3-center 2-electron bond in a Lewis structure?

How would you write $\ce{PCl5}$ or other hyper-conjugate molecules as a Lewis structure that indicates 3-center 2-electron bonds? I have seen depictions [1] for transition metal complexes but not for ...
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2answers
3k views

How to convert wedge–dash structure into Fischer projection? [closed]

I am very confused when a compound with more than one chiral centre is given. How to find whether the two compounds are enantiomers or diasteromers? Please also explain how to convert more than one ...
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2answers
144 views

Y-axis of the reaction co-ordinate graph

In the graph of the reaction co-ordinate, is the $y$-axis that is used $∆H,$ $∆U$ or $∆G$?
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Multiplicity letter codes for large amount of states

Well, let's say we have a large amount of states computed (e.g. over 50), all with the same multiplicity. So, our ground state can be $X^2\Sigma^+_g$ and we can continue with $B^2, C^2$ etc. as ...
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318 views

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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2answers
985 views

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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1answer
145 views

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 ...
14
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1answer
955 views

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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3answers
5k views

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 ...
5
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1answer
125 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?
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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
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1answer
237 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
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1answer
194 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?
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1answer
59 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
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1answer
538 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 ...
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2answers
242 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 ...
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3answers
482 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
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1answer
246 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 ...
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1answer
29 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 ...
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1answer
104 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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60 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), ...
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1answer
932 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
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2answers
347 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 ...
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2answers
172 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....
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1answer
228 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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32 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 ...
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2answers
791 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
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1answer
142 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
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1answer
70 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
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1answer
43 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{...
4
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1answer
133 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 $\...
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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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1answer
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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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1answer
376 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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1answer
2k 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, $\ce{2H2SO4}$.
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1answer
81 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
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1answer
54 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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2answers
1k 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 $\ce{Ca}^{2+}$?...
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20 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?
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1answer
155 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 ...