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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1answer
398 views

Why is a double bond not formed with oxygen when reacting this molecule with PCC?

In my textbook it says that when reacted with PCC, primary alcohols produce an aldehyde. Why is this example different? I do not see any double bonds.
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212 views

How do I correctly typeset metastable radionuclide symbols?

Does anyone know if there is an officially sanctioned way to typeset symbols like technetium-99m (99Tcm or 99mTc)? I have seen both, although in more recent publications, I think, the latter ...
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1answer
3k views

How to label atoms or groups “backwards” in ChemDraw

I'm trying to draw L-tyrosine with the hydroxyl part of the phenol as HO instead of OH as it appears in the ChemDraw image. ...
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1answer
18k views

What does the unit M stand for? [closed]

What does $\mathrm{M}$ signify in this pH calculation? To me, it just seems to be a random variable. For example: $\ce{[H+]} = 1.0\times10^{-7}~\mathrm{M}$ I am not sure what the $\mathrm{M}$ is ...
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3answers
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DL vs dl notation [closed]

As the L-isomer of glucose, it is the enantiomer of the more common D-glucose. Source: Wikipedia As far as I know enantiomers or Optical isomers are non superimposable mirror image structures with ...
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3answers
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What is the formally correct notation of t-Bu, i-Pr, p-NO2, n-Bu, a-HCl, etc.?

In chemical notation, can I safely assume that the notation of a single lower-case latin character followed by a hyphen followed by an Element upper-case latin character (and possibly more characters)...
5
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1answer
265 views

What is this SMILES notation: C[Si](C)C |^1:1|

When converting InCHI to canonical SMILES using Indigo, I will occasionally get an output SMILES string like this: C[Si](C)C |^1:1| What does the "|^1:1|" part ...
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1answer
7k views

What is difference between T1g and T2g?

I know that the “$\mathrm{g}$” stands for symmetry of octahedral shape, but how are labels “1” and “2” given in $\mathrm{A_{1g}}$ and $\mathrm{A_{2g}}$ representations too… Is it related to group ...
23
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3answers
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What does the circle inscribed in a benzene ring represent?

I have seen benzene being depicted in two different ways: For the right-hand structure, does the inscribed circle represent the movement of double bonds or electrons?
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1answer
58 views

Naming an Ion with respect to its oxidation state

When identifying compounds, where certain elements are in various oxidation states we write the oxidation state in Roman numbers after it. Does the same go for ions? What would the correct way of ...
2
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1answer
541 views

Molar heat capacity and heat capacity

Is molar heat capacity and heat capacity at constant volume both represented by $C_v$? at constant pressure both represented by $C_p$?
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1answer
102 views

Is there a convention as to what order to write reactants and products in a reaction?

When doing homework, it can be time-consuming to check the answers in a redox reaction due to different order of the reactants and products. For example, while $$\ce{2MnO4- + 5Fe^2+ + 16H+ -> 2Mn^...
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1answer
2k views

Interpreting notation format 1.64E-02 from particulate emission data

I'm doing a research project for school on air pollution and part of it is studying pollution caused by aviation and I have found a table of data for the emission indices of various pollutants but I'm ...
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0answers
149 views

How to know when subscripts refer to charges or not [closed]

My question is very easy. Sometimes to determine to charge of a compound you multiply the charge by the number of ions you have of that element. But sometimes it seems as if you don't do it this way. ...
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1answer
97 views

How to differentiate the notation of a compounds charge and an anions oxidations state?

I have had the case a few times. Being given something of this form: $$\ce{Cr2O7^2-}$$ How do I know whether the $2-$ is referring to the oxidation of the oxygen anion or the charge of the whole ...
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1answer
7k views

What are the correct equilibrium arrows?

I was recently subject to some atrocious teaching. One of the gems that found me was the equilibrium arrow usage. I am accustomed to write $\ce{<=>}$. Yet, the entire class had to use ⇆ ...
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2answers
349 views

Why do some diagrams of some molecules show the bonds of only some of their submolecules?

In the diagram of ATP below this paragraph there are no lines between the atoms in the $\ce{NH2}$ molecule or in the $\ce{OH}$ molecules; however, there are lines between all the other atoms. Does the ...
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2answers
4k views

Why is the minus sign (-) not allowed in reaction equations?

Recently in my chemistry class, the teacher told us that while writing "half equations" (such as a sodium atom losing one electron to form a sodium ion) we were not to use a simple minus sign. We were ...
5
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1answer
233 views

Typesetting oxidation state and charge simultaneously

I'm currently trying to typeset the ion $\ce{Cr2O7^{2-}}$ with oxidation numbers on. My first thought was to put the oxidation state above the atom, but according to IUPAC, the oxidation state should ...
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1answer
94 views

What does A485 mean? And what does the values on the y-axis expresses?

This question is from past exam paper. I don't want an answer to the multiple choice question below, I just want to understand what A485 means in the context of the question.
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1answer
108 views

What does this curve over the C-B bond mean?

I have come across this notation in a question I am trying to answer and am unsure of what exactly it means, can anyone clarify what this represents?
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2answers
2k views

What is the role of the slash (“/”) in chemical reactions?

I have always been confused about the role of slash in chemical reactions. In some reactions, e.g. $\ce{NaBH4}/\ce{OH-}$ it means we use both compounds, right? And in reactions where we write $\ce{...
2
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1answer
195 views

General notation for one of the d-orbitals

What is the general notation to represent the d-orbital with $l=2$, $m_l=0$, i.e. the orbital normally referred to as $\mathrm{d}_{z^2}$. To elaborate more, this orbital can be ordered in various ways ...
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1answer
434 views

Writing Mass Balance Equations

I was curious if there is a specific reason why when writing mass balance reactions we always leave a $\ce{H+}$ on the left side of the equation as the professor did not explain so, or is it just ...
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1answer
58 views

The usage of 'limiting composition'

I am reading wikipedia page on Molybdenum bronze and they mention this: Blue bronzes, with limiting composition $\ce{A_{0.3}MoO3}$ that is, $\ce{A_3Mo10O30}$. I used to see these fractional ...
5
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1answer
85 views

How to calculate and denote small uncertainties?

I am writing a report and I'm stuck on determining how to write the uncertainty. I have this: $$1.0 \times \left( 0.1000 \pm 0.0005 \right).$$ If I multiply the values, I need to keep two ...
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2answers
218 views

Phase subscript for supercritical reagent?

When writing a chemical reaction, one can use subscripts to denote the phase of a reagent, e.g. $\ce{SiO2 (s)}$, $\ce{H2O (l)}$, $\ce{F2 (g)}$ or $\ce{Na^+ (aq)}$. However, I need to write a reaction ...
5
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1answer
6k views

Is there a consensus how to report coupling patterns greater than quartets?

When analysing NMR spectra, every student at one time during their chemistry studies learns about vicinal coupling and that it produces the characteristic signal shapes of proton spectra. The ...
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2answers
382 views

Significant figures addition vs multiplication

I was finding the molecular weight of $\ce{Br2}$ the other day and noticed that if I add the weight of $\ce{Br}$ to itself, $79.90+79.90=159.80$, that answer for the weight has $5$ significant figures....
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1answer
137 views

Hill system with isotopologue

I'd like to use Hill notation (i.e. CH, then alphabetical), but I am not sure how to include isotopologues (i.e. carbon-13) in this notation. For example, what would be the preferred form of ...
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2answers
8k views

Correctness of writing H3C as opposed to CH3 in a carbon chain

I have been studying alkanes, alkenes & alkynes for a while, and I see in the examples that all the basic structural formulas start with $\ce{CH3}$, then $\ce{CH2}$, and the last carbon atom is $\...
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3answers
1k views

Superscript open circle notation in formula

I may be only a physicist but I'm familiar with the superscripted dot to indicate a radical. In a paper I'm reading the authors have also used a superscripted open circle. I can't find any reference ...
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1answer
271 views

Dissociation reaction notation

This equation has been described as an equilibrium in an article, how would you explain it to someone with not a lot of understanding of it. The equation is: $\ce{CH3COOH <-> CH3COO- + H+}$ ...
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3answers
8k views

Which one is the best notation for sodium acetate

I have seen two different notations for sodium acetate. The first one is: $$\text{NaCH}_3\text{COO}$$ The second one is: $$\text{CH}_3\text{COONa}$$ Now I'm confused, which one is the best to use?
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1answer
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How are point group character tables typeset correctly?

I want to know how to typeset character tables of point groups correctly. Consider the following two extremes using the $C_{\text{2v}}$ (or is it $\text{C}_{\text{2v}}$?) point group as an example. ...
6
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1answer
2k views

Kröger-Vink notation for defect reactions

In the Kröger-Vink notation the effective charge $c$ is marked as superscript while the site location $s$ is marked as subscript on the atom itself $\ce{A}$: $$\ce{A^{c}_{s}}$$ As far as I have ...
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2answers
1k views

Why does my professor use both the upper, and the lower, case literal of a letter to symbolize the same concept?

In one of our slides, the professor has written $ \Delta E_{sys} = -\Delta e_{sur}$ Where $E_{sys}$ symbolizes the energy of a given system, and $e_{sur}$ symbolizes the energy of the ...
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1answer
2k views

What is the meaning of the “colon” notation in chemical formulas?

For example PEDOT:PSS and P3HT:PCBM.
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6answers
4k views

May I treat units (e.g. joules, grams, etc.) in equations as variables?

Suppose I have two units, Tonks, $T$, and Borks, $B$, as well as the equation $\frac{50T}{20B}=x$. May I manipulate the equation as though $T$ and $B$ were the kinds of symbols that we learned to ...
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2answers
356 views

Proper dash to use for negative charge

What type of dash does one use when indicating something like F$^{-}$? I assumed it was a minus, since you indicate positive charge with a +, but there is one professor I know who insists that it ...
5
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0answers
119 views

Raoult's law: is the molar fraction the molar fraction in the entire system?

I have two physical chemistry textbooks, one by Atkins and one by Levine, which seem to differ in their notation used when describing Raoult's law. Atkins talks about the molar fraction term in ...
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1answer
12k views

Why do we sometimes write reactants above the reaction arrow?

We write: \[\ce{Alcohol ->[\ce{KMnO4}] Acid}\] The alcohol forms a carboxylic acid, i.e. gains an $\ce{O}$ from $\ce{KMnO4}$. This means $\ce{KMnO4}$ is a reactant! Then why is it written above the ...
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3answers
75k views

What is the meaning of the “dot” notation in chemical formulas?

For example for 4 given elements A,B,C,D, what's the meaning of $\text{AB} \cdot x \text{CD}$?
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1answer
86 views

Is there any abbreviation for hydrates?

I'm getting tired of writing out the full formulas for hydrates, adding $\ce{.$x$\,H2O}$ to all formulas. I'm wondering if there's standard shorthand for these.
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1answer
105 views

Single line equilibria notation

I'm reading a paper with a reaction scheme where an enzyme binds loosely to inhibitor reversibly and then the Enzyme-Inhibitor complex undergoes another reversible conformational change to a tightly ...
3
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1answer
894 views

X[Y|Z] formulas

I often find formulas of minerals where some element symbols are grouped within square brackets and separated by a vertical bar. An example can be brochantite, whose formula I find expressed as $\ce{...
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1answer
635 views

What would be SMILES notation for a compound with delocalized bonding?

For example, the cyclopentadienyl rings in ferrocene $\ce{Fe(}\eta^5 \ce{-C5H5)2}$ are often drawn with delocalized electron circles in them instead of explicit pi bonds. The Wikipedia article for ...
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3answers
2k views

Proper typography of “NOx”

I am a journal typesetter, and recently I came to a problem that I'm not sure I know to solve. The question is how to properly typeset the "NOx" abbreviation for nitrogen oxides. Which is ...
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1answer
2k views

What is the correct chemical formula for monosodium glutamate?

Recently, I am interested with home materials and I discover that the chemical symbol for MSG or monosodium glutamate is $\ce{C5H8NO4Na}$. My problem is shouldn't it be $\ce{NaC5H8NO4}$ as we always ...
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4answers
45k views

What does the ‘−1’ superscript mean in units?

For example, the rate of a chemical reaction can be expressed in $\mathrm{mol}/\mathrm{L}^{-1}/\mathrm{sec}^{-1}$. Why is it ‘−1’ and not, say, ‘−2’? Does it change the meaning if the minus is removed ...