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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Meaning of the symbol “$\Delta_\mathrm{sub}H^\circ[\ce{I2,s}]$”

One of the back exercises (13(C)) from the book for practice provided at my school asked whether the following relation is true: $\Delta_\mathrm{f}H^\circ(\ce{I2,g}) = \Delta_\mathrm{sub}H^\circ[\ce{...
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Reagent notation: meaning of dash(-) and line(|) or slash(\) in reagents

I've seen a lot of reagents which have a slash between two compounds, such as Lindlar's catalyst which is $\ce{H2}$ along with $\ce{Pd|BaSO4}$. I know that the sulphur is a poison here but in general, ...
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Why is U the symbol for lattice energy?

I often see $U$ or even $\Delta U$ being the symbol for lattice energy. Why is that? Does it refer to internal energy?
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What are t2g and eg in CFT?

In the crystal field theory (CFT), when the splitting of the d-orbital occurs, it gets divided into two parts. The upper part with higher energy is the $\mathrm{e_g}$ and the lower part with lower ...
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2answers
470 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 ...
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1answer
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How much is 1 mμg?

So I stumbled on a research paper by Okuda and Takedatsu [1] that uses mμg as a symbol for the mass unit. I couldn't find anything about this measure unit anywhere except a recommendation not to use ...
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138 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?...
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1answer
119 views

What is the correct formula for diamminechloridonitrito-n-platinum(II)?

Is the correct formula for diamminechloridonitrito-n-platinum(II) $\ce{[Pt(NH3)2Cl(NO2)]}$ or $\ce{[PtCl(NH3)2(NO2)]}$? I was taught that the sequence of symbols within the coordination entity should ...
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What is the difference between these two formulas for pH of weak acids?

In the German Wikipedia article on $\mathrm{pH}$, I found the following formula for calculating the $\mathrm{pH}$ of weak acids (which are there defined of having $4.5 < \mathrm{p}K_\mathrm{a} < ...
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Reference for molecular orbital theory [duplicate]

I am studying electron collision with molecules, and came across with notation like this $\left(\mathrm{B}^{1} \Sigma_{u}^{+}, \mathrm{c}^{3} \Pi_{u}, \mathrm{a}^{3} \Sigma_{g}^{+}, \mathrm{C}^{1} \...
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Are Alloy Compositions Given in Weight Percent or Atom Percent

Often times I see alloys described like this, Lockalloy is an alloy that consists of 62% beryllium and 38% aluminum Are the precentages mentioned here in weight percent or atom percent? Is there a ...
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When writing the net ionic equation, if one of the products ionizes, what is the most appropriate way to account for this in the answer?

Take these two practice problems and their solutions from Ebbing (8th ed) that involve completing the molecular equation, then writing the net ionic equation: 4.42a: $\ce{Ca(OH)2(aq) + 2H2SO4(aq) ->...
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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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What do γ (gamma) and λ (lambda) mean in organic chemistry?

From the Wikipedia entry on Cyhalothrin: Pyrethroids such as cyhalothrin are often preferred as an active ingredient in agricultural insecticides because they are more cost-effective and longer acting ...
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Type of diagram and ordering of bonds used to depict a glucose molecule

I find these type of diagrams easier to consult when building molecules using a 'molecular building kit'. Is there a name for this type of diagram? For the glucose molecule (in the above diagram), I ...
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What did I do wrong in my orbital notation for this Os (Osmium) question?

I was given a question where I had to write the orbital notation of Osmium (Os) and I got it wrong. The question: 6s2 --> ↑↓ 4f --> ↑↓↑↓↑↓↑↓↑↓↑↓↑↓ 5d6 --> ↑↓↑↓↑↑ The arrows above are my ...
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2answers
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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
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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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Three stacked arrows, what does it signify?

I was checking the mechanism for the Lossen Rearrangement, when I came across the chemical reaction denoted as follows: I couldn't find any resource where this notation was talked about. What do the ...
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1answer
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What does A. R. in A. R. sodium nitrite mean?

I'm reading about a reaction from a 1970s organic chemistry book. It references A. R. sodium nitrite. What does the A. R. mean? I see from online that "Ar" means aromatic ring. Is that the ...
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Writing water as a reactant in acid/base dissociation (Brønsted Lowry)?

The dissociation of $\ce{HCl}$ in water is written as: $$\ce{HCl (aq) -> H+ (aq) + Cl- (aq)} \tag{1}$$ Sometimes we also include $\ce{H2O}$ as a reactant to stress the fact that the protons are not ...
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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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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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Rules to follow while writing a chemical formula for polyatomic ions

In Science, textbook for class IX, chapter $3$ [1,p.38], it states: The rules that you have to follow while writing a chemical formula are as follows: in compounds formed with polyatomic ions, the ...
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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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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 ...
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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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644 views

What does K° signify in this reaction?

What does the K° signify in the above reaction. Is it just a typo, or is it supposed to symbolize something? EDIT: This screenshot is from the solutions manual. In the original textbook, the author ...
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1answer
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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 $\mathrm{S_N1'}$ ($\mathrm{S_N1}$...
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592 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 - ...
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1answer
125 views

Convention in electrochemical cell notation

While writing the cell notation for a cell, doesn't one have to write the two states in which a species exists in a sequence appropriate to the reaction in which they participate? For example, in the ...
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72 views

Proper notation of doubly charged ions

I have always notated doubly charged ions with a superscript $++,$ such as $\ce{He^{++}}.$ For more highly-charged ions I would denote them with the number of charges, such as $\ce{Pt^{4+}}.$ ...
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2answers
504 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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2answers
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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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What is the “‡” symbol meaning in a reaction mechanism?

I was studying hydroboration from Clayden's Organic Chemistry [1, p. 1281] and the transition state had “‡” symbol in the upper right corner of the activated complex: We know that this is not the ...
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2answers
124 views

How to identify if a material is perovskite or not?

This is more of a materials science question, but I believe many of you have referred NIST Inorganic Crystal Structure Database (ICSD) database. I am collecting a database of perovskite materials and ...
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803 views

What is the @ symbol used for in material science?

I came across the phrase "Silicone Rubber/Paraffin@Silicon Dioxide" also written as $\ce{SR/pa@SiO2}$, utilising the @ symbol. How can I understand what this means?...
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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 ...
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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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What is the correct electron dot notation of carbon?

My book says that the dot notation for Lewis structure of carbon has 2 possible ways: two dots on the right, one on the top, one on the left one dot on all four sides Why are both of these correct? ...
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Notation in atomic structure

In the book, The theory of atomic structure and spectra, Robert D. Cowan says that the allowed terms of $p^2$ are $^1S$, $^1D$, $^3P$ and so the possible terms of $p^2 + p\quad$ (obtained by using the ...
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Writing a organic reaction in different form

Can I write this reaction $$\ce{A + B ->[\ce{X}] C + D ->[\ce{Y}] E + F}$$ as $$\ce{A + B ->[\ce{(1) X}][\ce{(2) Y}] E + F}$$ Can I write any organic reaction in this way or are there any ...
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How do I denote a measurement with a margin of error using ±?

I am trying to express a quantity that is measured to be $\pu{0.75 mL}$, but could be anywhere between $\pu{0.7 mL}$ and $\pu{0.8 mL}$. Is this the correct way to do it? $$\pu{0.75 mL} \pm \pu{0.05 ...
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1answer
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Connection between irreducible representations and electronic states in diatomic molecules

I am trying to understand the connection between irreducible representations and molecular electronic states. To explain the problem: I found some potential energy curves (PECs) for $\ce{N2+}$ in the ...
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2answers
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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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1answer
40 views

Question on notation

Here, when they write $v/(\mathrm{mol\ s^{-1}\ (kg\ \text{protein})^{-1}})$ is $0.30$ for the first row first column, do they mean that the value is $0.30\ \mathrm{mol\ s^{-1}\ (kg\ \text{protein})^{-...
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1answer
284 views

Why do we write electrode potentials next to chemical reactions? [closed]

We might have a half cell consisting of the redox couple $\ce{Ag+}/\ce{Ag}$, which for example's sake might be fixed to be at the cathode (i.e. undergoing reduction). The reaction at the cathode is ...
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1answer
1k views

What does (sol) in a chemical equation mean?

I'm reading Shrivers Inorganic Chemistry book and some of the equations have a (sol) state on them. I'm sure the book has already defined this but I cannot find where. Examples: \begin{align} \ce{[...
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1answer
42 views

Formating a chemical equation - Physical states

I study chemistry in an University and I have two professors that says opposing things. One says that the physical state must be subscribed (1 at the picture) and other that it must be written to the ...
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1answer
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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 ...

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