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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10
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1answer
363 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 ...
12
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1answer
142 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
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1answer
631 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
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1answer
185 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
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0answers
68 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 ...
9
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1answer
6k views

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 $\mathrm{S_N1'}$ ($\mathrm{S_N1}$...
9
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1answer
420 views

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 ...
3
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2answers
3k views

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 ...
3
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2answers
2k 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
2k 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
818 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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0answers
120 views

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 ...
4
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1answer
2k views

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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0answers
1k 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 ...
5
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1answer
7k views

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? $$\ce{N2 + 8H + 8e- + 16 ATP -> 2NH3 + H2 + 16ADP + 16 P_{i}}$$
7
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1answer
119 views

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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2answers
4k views

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 ...
4
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1answer
125 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,...
9
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2answers
1k views

Is “amount of substance” the same thing as “number of moles”?

Background: Amount of substance is a fundamental physical quantity which has mole (mol) as it's SI unit. Therefore all expressions for amount of substance should have the unit mole on simplification. ...
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2answers
36 views

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.
5
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2answers
1k 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 ...
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3answers
4k views

Drawing the condensed structure of ethylcyclobutane

The IUPAC name for this is ethylcyclobutane. I know that the formula is $\ce{C6H12}$. I have no problems drawing the skeletal structure, but I have a little difficulty drawing the condensed structure....
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2answers
1k views

Can isotopes of a given element be represented by different symbols?

Can isotopes of any given element be represented using a completely different chemical symbol? What's the IUPAC's take on this? Sure, ordinarily you would add the isotope's mass as a superscript to ...
1
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1answer
9k views

What is the meaning of n-Pr and i-Pr?

Apologies in advance, I have a background in physics, so this question might seem awfully simple. Anyway, I am interested in the chiral spin selectivity effect in organic molecules, and have read a ...
2
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1answer
502 views

Chemical reaction notation in differential equations

It's common to see chemical reactions in this notation: $A \overset{k}{\longrightarrow} \emptyset$ which means $A$ is degraded with rate $k$. What's the proper way to convert this to an ordinary ...
0
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1answer
335 views

How do we know the number of atoms in an inorganic compound? [duplicate]

How do we know the number of atoms in an inorganic compound? If there's a question like 'Write the chemical formula for sulfur dioxide', the only thing I managed to do is answer '$\ce{SO}$'. I don't ...
6
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1answer
124 views

How to calculate molar mass of (6)UO2+2D and (6)UO2OH+D?

For a hydrogeochemistry project, I want to calculate the molar masses of some compounds. I came across a problem when encountering species like (6)UO2+2D (aq) and <...
5
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2answers
3k views

What does the plus-minus sign with a value in parentheses mean?

I always see the plus-minus sign with a value in parentheses after a physical property is described such as melting and boiling point, like this: $$\text{Melting point }(\pm 1~^\circ\mathrm{C})$$ ...
8
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1answer
445 views

What does the colon in µ-η2:η2-O2 mean?

In the formula $\ce{[nBu4N]2[(UO2)2(\mu-\eta^2:\eta^2-O2)(NO3)2(\mu-Au(CN)2)2]}$, what does the colon stand for? Is this an official notation?
10
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1answer
116 views

Is there a convention for breaking chemical formulae across lines?

I found a chat where a user asked for chemical formulae to be broken across lines (with LaTeX/mhchem). I could imagine offering a switch to allow this. But only, if line-breaking within formulae is ...
5
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1answer
87 views

Should an entire compound or just the redox-active element be written in redox pairs?

For oxidant/reductants and conjugate pairs, for example $\ce{MnO2 -> Mn^2+}$, do we write $\ce{Mn^4+}$ or $\ce{MnO2}$ as the oxidant? Websites conflicts what my text book says, because it appears ...
2
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1answer
299 views

Wavenumber range reversed in IR spectroscopy

I recently stumbled upon a result table from an IR spectroscopy, that is an image full of peaks. The goal was to decide which peak belongs to which group by looking up the intervals in a related table....
3
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0answers
330 views

Various meanings of Ka, Kb etc

A little while back, I introduced the feature to mhchem to properly format $K$ constant variables, like $\ce{Ka}$ rendering as $K_\mathrm{a}$, ...
6
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1answer
87 views

Should compounds in a generic reaction be italicised (typography)?

As of recent, I provided an answer to the question Law of mass action & collision theory. Therein I wrote a generic reaction $$\ce{$r_1$R1 + $r_2$R2 + \ldots + $r_n$R_n <=> $p_1$P1 + $p_2$...
6
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0answers
94 views

Is it correct to use the symbols (l) and (g) in every reaction?

I know that this question might sound stupid to most of the people, but for a chemist noob like me is not very clear. So, here's the main question: Is it appropriate to use the symbols (l) for ...
9
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1answer
214 views

Typography of atomic orbital subscripts p_x

It the notation $\mathrm{p_x}$, $\mathrm{p_y}$ and $\mathrm{d_{x^2{-}y^2}}$, are the subscripts variables (and therefore should be in italics) or are they labels (labels for directions, I suppose, and ...
10
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1answer
575 views

Syntax and Typography of Atomic Orbitals

For mhchem (i.e. the \ce command you use here), I want to improve the support for atomic orbitals. (Reason: I see it quite often used here.) But only a few things ...
4
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1answer
113 views

Phase description for a substance dissolved in a solvent other than water?

I'm trying to write an equation for which I have $\ce{CuI}$ dissolved in acetonitrile. Usually if you have a salt dissolved in water you can denote that using $\ce{(aq)}$, but is there a notation for ...
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2answers
685 views

Notation of hydrogen

$$\ce{e- + H2O -> [H$\cdot$] + HO-}$$ I was a little confused on the notation of the hydrogen in brackets ([H]) in the product side of the reaction. Why is there a dot next to it and what does it ...
3
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1answer
244 views

Use of subscript cc for HCl and H2SO4

Does the subscript $\ce{X}_{cc}$ mean concentrated? I have never seen this notation. How often is it used and what are the general guidelines to denoting concentrated reagents?
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4answers
3k views

Why is the letter J omitted in the spdf… sequence?

Under spherical symmetry, the irreducible representations corresponding to $L = 0, 1, 2, \cdots$ are assigned the letters $\mathrm{S}, \mathrm{P}, \mathrm{D}, \mathrm{F}, \cdots$ after which the ...
2
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2answers
518 views

pH notation in text

When referring to units of pH in continuous text (i.e. not in a table), which is the recommended usage? pH 7 to pH 8 pH 7 to 8 What about when the term "pH" has already been mentioned in the text? ...
5
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0answers
155 views

Side chain formation in polymerisation of ethylene

I am having difficulty understanding (or at least need confirmation of my understanding) of this diagram regarding the formation of sidechains of polyethylene. If someone could explain it, that would ...
32
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6answers
20k views

Why do chemistry and physics have different sign convention in thermodynamics?

In physics class, we write the first law of thermodynamics as $\mathrm dU =\mathrm dQ - \mathrm dW$ and in the physical chemistry class, we write the same law as $\mathrm dU =\mathrm dQ + \mathrm dW$. ...
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5answers
97k views

What is the difference between O & O2

What is the difference between $\ce{O}$ and $\ce{O2}$. If C is carbon and then why $\ce{O2}$ is oxygen.
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1answer
284 views

Is it Cu²⁺ or Cu⁺²? [duplicate]

Is $\ce{Cu^{2+}}$ or $\ce{Cu^{+2}}$ correct? In my book the author uses both but at different places.
3
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1answer
2k views

What does 10 Vols mean?

I am currently working on a project and the protocol says the following, "Wash resin 3 times 10 vols of the extract buffer." This is very confusing to me and I am not exactly sure what the 10 vols ...
0
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1answer
2k views

Should moderately soluble compounds like calcium hydroxide be denoted (aq) or (s)?

I'm learning to write balanced molecular and ionic equations. For "moderately soluble" compounds such as calcium hydroxide, how do I know whether to write the state symbol as (aq) or (s)? This is the ...
2
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1answer
1k views

Brackets in chemical formulas

When you have brackets such as $\ce{Zn(NO3)2}$, if there is a coefficient around the formula such as $\ce{2Zn(NO3)2}$, how would you read this? Would there be 2 zinc atoms, 4 nitrogen and 12 oxygen ...
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1answer
2k views

What do dashes mean in chemical formulas?

I'm working on summarizing some research for an essay; here's the main article. The basic premise is making nanoparticles from gold and iron(III) oxide that have properties of both gold and iron. ...