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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974 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 ...
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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? $$\ce{N2 + 8H + 8e- + 16 ATP -> 2NH3 + H2 + 16ADP + 16 P_{i}}$$
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1answer
118 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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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 ...
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1answer
122 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,...
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2answers
737 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
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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.
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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
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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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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 ...
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1answer
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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 ...
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1answer
451 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 ...
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1answer
320 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 ...
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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 <...
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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: $$\text{Melting point }(\pm 1~^\circ\mathrm{C})$$ ...
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1answer
375 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?
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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
83 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 ...
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1answer
236 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....
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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 $K_\mathrm{a}$, ...
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1answer
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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 + $p_2$...
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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 ...
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1answer
199 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 ...
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1answer
545 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 ...
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1answer
87 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
375 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 ...
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1answer
227 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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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 ...
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2answers
476 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? ...
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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 ...
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6answers
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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
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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
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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.
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1answer
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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 ...
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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 ...
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1answer
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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
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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. ...
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1answer
910 views

Letter codes in molecular term symbols

I'm trying to find an explanation for the letter codes (X, A, B, C, etc) when you get a term symbol like this $$X\,{}^3{\Sigma}^-_g$$ Can anyone point me to some literature that explains these ...
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2answers
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What databases or repositories are there that have generalized SMILES for functional groups?

Does a resource exist that has the SMILES formula of the generalized pattern that represents the group? For instance: I have the aldehydes group, which has the pattern: ...
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1answer
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How to write reaction equations for the reaction of calcium and dilute nitric acid?

Normally metals react with dilute acid to form a salt and evolve hydrogen gas but I have read that hydrogen gas is not evolved when a metal reacts with nitric acid (because Nitric acid is a strong ...
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1answer
3k views

What is the difference between λ and Λ with regard to molar conductivity?

I came across these equations (boxed in red) in a book: $$ \begin{align} &\therefore & t_\mathrm{c} &= \frac{u_\mathrm{c}}{u_\mathrm{c} + u_\mathrm{a}}\\ &\text{and} & t_\mathrm{...
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2answers
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Rounding of atomic weight isotopes

When we look at atomic mass, for example, $\ce{^134Ba}$ (barium) has a mass of $133.90 \,\mathrm{Da}$. Why is this rounded to $134 \,\mathrm{Da}$? This is shown in my book.
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1answer
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What does the symbol ϕ mean in skeletal formulae?

I was given this formula by my A-level teacher and was curious as to what it means. It seems to be the Greek letter phi. I have searched online and have not been successful. Any help would be greatly ...
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2answers
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What does a number in brackets after another number mean? I.e. 21(1)cm-1

What does the number in brackets mean in these two examples? $$21(1)\ \mathrm{cm^{-1}}$$ and $$1.0(3)\times10^{-7}$$
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2answers
473 views

How to distinguish first excited state and second excited state?

I am learning excited state calculation. In this paper, the author use "$D_0$","$D_1$" represent excited state of nitrate radical. I know the symbol such as "$D_1$","$T_2$" means first excited ...
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2answers
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What do these labels for molecular electronic states mean?

What do these symbols mean in excited states? $${}^2\!A_2,{}^2\!B_1,{}^4\!A''$$ I am confused with these representations, found in the abstract of this paper. I think it is kind of a representation ...
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2answers
598 views

Is there an abbreviation for “something bulky”?

I want to draw a scheme that indicates the difference between the products formed in a reaction with a molecule that will form one thing when it has methyl or hydrogen substitution, but another thing ...
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2answers
140 views

When does a reaction equation require the reversible sign and when does it not?

Sometimes my professor puts the $\to$ symbol and sometimes he uses $\leftrightharpoons$. How do I know which to use? I get that one means the reaction only heads one way while the other means that the ...
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1answer
2k views

What do curly brackets {} mean?

I learned that square brackets ex: $[\ce{H2O}]$ can be used to denote the concentration of water molecules in a fluid. The notation used much in equilibrium problems and such. However, sometimes I ...
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1answer
1k views

Typography of Orbitals

For mhchem, I need to decide on a typographical representation of orbitals. Wikipedia tells me, there are atomic orbitals with letters s, p, d, f and g. In a later ...