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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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What does ‘S/A’ mean in SMARTS pattern when using Chemicalize to draw the chemical structure?

I am still new to the SMARTS annotation. I am wondering what does S/A’ mean on the bond labeling drawn with Chemicalize using SMARTS [!#1]c1n[cH]nc([!#1])c1[!#1]? ...
tassaneel's user avatar
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3 votes
1 answer
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What does ‘(A)’ mean in SMARTS pattern when using Chemicalize to draw the chemical structure?

I am not quite sure what ‘(A)’ could mean for the carbon atom when writing the SMARTS CCN(C)C using Chemicalize to draw the chemical structure below. Can anyone ...
tassaneel's user avatar
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0 answers
34 views

Meaning of letter K in chemistry conventions [duplicate]

The letter "K" is usually used as chemistry (or statistics/ physics) conventions, take the equilibrium constant (Kc) and rate constant (k) as two prime examples. Are there any reasons why &...
Chemistry student's user avatar
5 votes
2 answers
277 views

Is there a symbol or representation for tolyl groups as there is for the phenyl group?

Is there a symbol or representation for tolyl groups as there is for the phenyl group? Phenyl group is often represented by "Ph" when for a matter of space you can not draw the entire ...
Eduardo L. Gutiérrez's user avatar
11 votes
3 answers
2k views

Why can you "cancel out" chemical species from a chemical equation that appear on both sides of a chemical equation?

Why is it acceptable in chemistry to "cancel out" chemical species from a chemical equation that appear on both sides of a chemical equation (as reactants and as products)? On the one hand, ...
Nefeli 's user avatar
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0 answers
33 views

How do I denote a specific rovibrational transition?

I am using a linelist from HITRAN, which gives me a whole lot of extra data and I want to denote the transitions accurately. But I don't know what to use for rovibrational transitions. The following ...
Benvz's user avatar
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1 vote
2 answers
170 views

How to obtain the expression for residual Gibbs energy?

The property involved is Gibbs free energy, the equations that I wrote are presented in my text book Introduction to chemical engineering thermodynamics by Smith and Van Ness, Chapter 6. The thing is ...
jack gatz's user avatar
3 votes
1 answer
236 views

Parentheses use in non stoichiometric compounds

When should one use (or not) parentheses in writing the formula for non stoichiometric compounds. I mean, the mineral sphalerite is often represented by the formula $\ce{(Zn,Fe)S}$ and, all though I ...
liuzp's user avatar
  • 142
0 votes
1 answer
91 views

What is the meaning of "*" in this compound notation?

I am reading a book on hydrogen energy (handbook of hydrogen energy), and came across the following compound on the Cu-Cl thermochemical cycle: $$\ce{CuO\text{*}CuCl_2(s)}$$ What exactly is the role ...
RMS's user avatar
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-2 votes
1 answer
4k views

How to make bonds thicker in ChemDraw?

I often see molecules depicted using ChemDraw with all or selected bonds visibly thicker than those used with the style defined with ACS-1996 template. For example, see the PDF handouts for Baran's ...
Lanagan's user avatar
4 votes
2 answers
555 views

What do consecutive letters A and B in the 4th column of PDB file signify?

What do the consecutive A and B in the 4th column identify in a PDB file downloaded from rcsb.org? The molecule name is 3CZ3 (...
majumderS's user avatar
4 votes
0 answers
85 views

Notation for spectral density in experimental community

In an open quantum system setup where the system is coupled to infinite harmonic oscillators as bath (as in the Caldeira leggett model, for example), through the Hamiltonian, $$H = \frac{\hat{p}^2}{2m}...
Prem's user avatar
  • 91
4 votes
1 answer
279 views

Line Entry system like SMILES for metals?

SMILES is not designed for metallic compounds. Is there a similar ASCII line entry notation for metallic compounds, including repeating structure in space, &c.?
Sam's user avatar
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1 vote
0 answers
206 views

What is the point of the up arrow (↑) which shows "gas evolved" or "gas liberated", if you could just write the state symbol (g)? [closed]

What is the point of the up arrow (↑) which shows "gas evolved" or "gas liberated", if you could just write the state symbol (g)? And would you write the up arrows (↑) and down ...
JChips's user avatar
  • 29
1 vote
1 answer
140 views

Total vs. Partial derivatives in kinetics

I've recently seen partial derivatives in the velocity definition but in most cases is with total derivatives (infinitesimal change of concentration over infinitesimal change of time). Maybe is more ...
Jorge Bonifaz's user avatar
-1 votes
1 answer
179 views

Convention for writing concentration units

1st part of my question: Q) The concentration of an NaCl solution is 1M. Express this in percent wt. by vol. unit. Ans: $$\text{In %(w/v) unit}=\frac{58.5\pu g}{1000\pu{mL}}\times \frac{100}{100}=5.85\...
tryingtobeastoic's user avatar
-3 votes
1 answer
973 views

What does $n$ represent in "hydrated compound⋅nH2O"? [closed]

On Wikipedia it is written that in "hydrated compound⋅nH2O" $n$ is the number of water molecules per formula unit of the salt. I don't understand what that means and this is indicated in ...
Osmium's user avatar
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0 votes
0 answers
55 views

Notational inquiry regarding nuclear chemistry

I'm aware that the notation for an element (with a charge) is as follows: $$\large ^{~~~\text{mass number}}_{\text{atomic number}}(\text{element symbol})^{\text{charge}}$$ However, during beta decay (...
faycalki's user avatar
10 votes
4 answers
2k views

Chemical formulas with non-integer coefficients [duplicate]

Let's consider the composition $\ce{Hg_{0.7}Cd_{0.3}Te}$ which appears in my data. As I remember from my chemical knowledge it's not possible having non-integers numbers as coefficients of elements. ...
James Arten's user avatar
3 votes
1 answer
235 views

How are names for atomic orbitals with high $l$ generated?

I'm looking at Table of Real Spherical Harmonics and trying to understand how the names for the real orbitals are generated. Note that I'm a physicist. In chemistry parlance, I'm trying to come up ...
Jagerber48's user avatar
7 votes
1 answer
422 views

Caffeine molecule representation and orientation

Almost all the representations of the caffeine molecule that I've come across have the two rings drawn next to each other on the horizontal axis. Any particular reason for this? Would it be sacrilege ...
Zaph Brox's user avatar
  • 107
6 votes
1 answer
272 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_{...
AmphotericLewisAcid's user avatar
4 votes
2 answers
343 views

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?
xenoid's user avatar
  • 151
2 votes
1 answer
112 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 ...
mac179's user avatar
  • 319
0 votes
1 answer
339 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 ...
mac179's user avatar
  • 319
5 votes
1 answer
103 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 $...
Oded R.'s user avatar
  • 215
5 votes
0 answers
118 views

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 ...
user avatar
-4 votes
1 answer
127 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 $$...
Nomas's user avatar
  • 109
5 votes
0 answers
105 views

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 ...
Ian Hamilton's user avatar
8 votes
1 answer
326 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 ...
user avatar
1 vote
1 answer
528 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.
Thor Correia's user avatar
-2 votes
1 answer
385 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 $...
neurosciencecalc's user avatar
2 votes
2 answers
974 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 ...
Ritwik_Kumar's user avatar
2 votes
1 answer
79 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{...
Aseem Mittal's user avatar
2 votes
1 answer
486 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, ...
sam's user avatar
  • 149
2 votes
0 answers
497 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?
Quantonium's user avatar
23 votes
1 answer
6k views

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 ...
Andyba's user avatar
  • 349
2 votes
1 answer
740 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 ...
SJY's user avatar
  • 39
3 votes
1 answer
211 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} < ...
jng224's user avatar
  • 273
1 vote
0 answers
38 views

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} \...
amilton moreira's user avatar
2 votes
1 answer
1k views

Are alloy compositions given in weight percent or atomic percent

Often I see alloys described like this, Lockalloy is an alloy that consists of 62% beryllium and 38% aluminum Are the percentages mentioned here a weight percent (wt.%) or atomic percent (at.%)? Is ...
Terry Price's user avatar
3 votes
0 answers
584 views

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 ...
Kurt Hikes's user avatar
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-1 votes
1 answer
452 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 ...
noi.m's user avatar
  • 121
-1 votes
1 answer
559 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 ...
Audrey W.'s user avatar
2 votes
2 answers
152 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) ->...
neurosciencecalc's user avatar
6 votes
2 answers
2k views

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 ...
Safdar Faisal's user avatar
2 votes
1 answer
557 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 ...
GFL's user avatar
  • 211
2 votes
1 answer
630 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 ...
Mr. Feynman's user avatar
0 votes
2 answers
1k 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 ...
Programmer's user avatar
6 votes
2 answers
725 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 ...
gauri agrawal's user avatar

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