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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24 views

number notation with space in atomic mass

I'm self-educating myself in the periodic table and came across some number notations I am not familiar with. Also to clarify, I have no school background and English is not my native language. That ...
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249 views

Is there a canonical variable for period and group?

For example, "Z" is the standard symbol for atomic number. I'm writing a manuscript that uses the group and period of elements within some equations, and so far I'm just denoting them as $G_{...
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Meaning of $\ce{(Si,Al)}$ in $\ce{XY(Si,Al)2O6}$ [duplicate]

On the wikipedia page for pyroxene minerals, it says that pyroxenes have the general formula $\ce{XY(Si,Al)2O6}$, "where X represents calcium (Ca), sodium (Na), iron (Fe II) or magnesium (Mg) and ...
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Are there examples of molecular formulas with nested groups?

Sometimes a molecular formula is written using groups, for instance $\ce{Al2(SO4)3}$. Are there examples of formulas with nested groups, such as $\ce{ABC[MNO2(XYZ)4]3}$ or is this avoided?
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56 views

Unique notation to search for compounds in PubChem and in Chembl

I am not a chemist, I come from a computer science background. I am working on a project related to computer-aided drug design. I have a list of chemical compounds in their SMILES notation, to which I ...
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50 views

How many characters does the SMILES notation uses? [closed]

I am not a chemist, in fact, I come from a computer science background, however, I am working on a project that involves using machine learning for SMILES generation. My question is, how many ...
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72 views

Symbol to denote a group which is either an oxygen atom or NH group

I'm drawing the generic structure of several different organic molecules in my thesis. They share some features, one of which is a carbonyl carbon attached to either an oxygen atom (i.e. ester) or an $...
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Meaning of $^2[\,1/2]$ terms in atomic spectroscopy

I was trying to analyze some atomic emission spectroscopy data and I encountered unfamiliar notation of the terms for me. Commonly, the electronic states of the atoms can be described by quantum ...
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73 views

Is Avogadro's constant equal to 1? [closed]

The mole is defined to be exactly $\mathrm{mol}=6.02214076\cdot 10^{23}$ entities. Avogadro's constant is defined as $N_A=6.02214076\cdot 10^{23}\mathrm{mol}^{-1}$. Then why is it not usual to write $$...
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Is a change in delta-delta-G typically notated as delta-delta-delta-G?

I'm currently writing a research paper, and need to refer to a difference between $\Delta{\Delta}G$s. The naive way to notate this would be $\Delta{\Delta}{\Delta}G$, but that looks cumbersome and ...
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108 views

Is “double dot” (“··”) notation used for a double radical?

I wondered if this was a typo in the notes given to me. I haven’t come across notation like this before: Branching — steps in which number of radicals increases (can lead to explosion) $$\ce{H^. + O2 ...
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59 views

How is electron-impact mass spectrometry data formally reported?

NMR data has the following format when reported in a paper: How would I go about reporting my EIMS data formally? I tried looking for documents online but couldn't find anything.
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87 views

Notation for inclusion of water in a dissolution equation

Earlier I had a student come by wanting to know how to show the dissolution of $\ce{NH4OH}$ in water. I would think we would just write it: $$\ce{NH4OH(aq) <=> NH3(aq) + H2O(l)}$$ I say this as $...
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What is the difference between these notations and terms?

I can't tell if they're being used interchangeably or if there's some nuanced difference betweem them. Here they are: $E^∘$ $E_0$ $E_h$ $E^⦵$ If I understand correctly, electrode potential is the same ...
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222 views

How to draw chair-form for trans-decalin (with slight variation)?

I understand how to draw chair form for trans-decalin (figure 1) for the usual structure, but I am having difficulty if taken as shown in figure 2 wherein the hydrogens at bridge-head carbons are in ...
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67 views

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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177 views

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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253 views

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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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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271 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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171 views

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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208 views

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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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 ...
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142 views

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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260 views

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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117 views

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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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
292 views

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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197 views

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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319 views

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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653 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
160 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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95 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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224 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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3k views

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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239 views

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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62 views

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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35 views

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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52 views

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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129 views

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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49 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
319 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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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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52 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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902 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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190 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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70 views

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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90 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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1k 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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