All Questions
Tagged with formatting or notation
65 questions
16
votes
3
answers
10k
views
Which one is the best notation for sodium acetate
I have seen two different notations for sodium acetate. The first one is:
$$\text{NaCH}_3\text{COO}$$
The second one is:
$$\text{CH}_3\text{COONa}$$
Now I'm confused, which one is the best to use?
- 329
44
votes
1
answer
7k
views
Why is methane's molecular formula conventionally "CH₄", while water is "H₂O" (among others)?
While revisiting some of my old notes about the Miller-Urey experiment, I stumbled across the "equation"...
Electricity + $\ce{CH4~/~ NH3~/~H2O~/~CO}$ = Amino Acids
This got me thinking.
...
- 1,752
36
votes
6
answers
32k
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 $\mathrm dU =\mathrm dQ + \mathrm dW$. ...
user31607
28
votes
3
answers
103k
views
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 $\text{AB} \cdot x \text{CD}$?
- 4,285
17
votes
1
answer
8k
views
How to interpret parts-per notations? Is 1 ppb equal to 1 μg/kg?
In an article I recently submitted, a reviewer asked that I provide a concentration in μg/kg instead of ppb (parts per billion), and mentions that the later is not correct. I am not a chemist, and I ...
- 281
23
votes
1
answer
808
views
Structure that breaks InChI
I am currently testing a piece of software that generates the InChI for a given structure. I also want to test error situations as end users will also deliver the mol files that will be used as input ...
- 365
4
votes
2
answers
1k
views
Y-axis of the reaction co-ordinate graph
In the graph of the reaction co-ordinate, is the $y$-axis that is used $∆H,$ $∆U$ or $∆G$?
- 1,246
37
votes
6
answers
6k
views
May I treat units (e.g. joules, grams, etc.) in equations as variables?
Suppose I have two units, Tonks, $T$, and Borks, $B$, as well as the equation $\frac{50T}{20B}=x$. May I manipulate the equation as though $T$ and $B$ were the kinds of symbols that we learned to ...
- 2,335
18
votes
2
answers
16k
views
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
$$1.0(3)\times10^{-7}$$
- 491
18
votes
2
answers
6k
views
Arrows used in chemical reactions
A point was raised about arrows used in a chemical reaction. I think we can all agree that $\ce{->}$ arrow in the reaction
$$\ce{A + B -> C} \tag{1}$$
means that the reaction goes in one ...
- 22.4k
17
votes
2
answers
4k
views
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 ...
- 711
5
votes
2
answers
1k
views
Significant figures addition vs multiplication
I was finding the molecular weight of $\ce{Br2}$ the other day and noticed that if I add the weight of $\ce{Br}$ to itself, $79.90+79.90=159.80$, that answer for the weight has $5$ significant figures....
- 201
36
votes
4
answers
6k
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 ...
- 71.9k
9
votes
1
answer
608
views
How to you show a 3-center 2-electron bond in a Lewis structure?
How would you write $\ce{PCl5}$ or other hyper-conjugate molecules as a Lewis structure that indicates 3-center 2-electron bonds?
I have seen depictions [1] for transition metal complexes but not for ...
- 42.3k
8
votes
1
answer
2k
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 ...
8
votes
3
answers
35k
views
DL vs dl notation [closed]
As the L-isomer of glucose, it is the enantiomer of the more common D-glucose.
Source: Wikipedia
As far as I know enantiomers or Optical isomers are non superimposable mirror image structures with ...
- 863
6
votes
2
answers
337
views
How do I correctly typeset metastable radionuclide symbols?
Does anyone know if there is an officially sanctioned way to typeset symbols like technetium-99m (99Tcm or 99mTc)? I have seen both, although in more recent publications, I think, the latter ...
- 63
29
votes
1
answer
108k
views
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 ...
- 1,693
12
votes
5
answers
146k
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.
- 295
12
votes
2
answers
5k
views
What is the role of the slash ("/") in chemical reactions?
I have always been confused about the role of slash in chemical reactions.
In some reactions, e.g. $\ce{NaBH4}/\ce{OH-}$ it means we use both compounds, right?
And in reactions where we write $\ce{...
- 1,051
12
votes
1
answer
5k
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 ...
- 223
7
votes
1
answer
169
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 $\ce{Al2O3}$?
- 929
5
votes
1
answer
2k
views
Significant figures used to imply stated error?
The question reads, " express each of the following quantities using significant figures to imply the stated error".
a)$2.3 \pm 0.001$
b)$1.989 \pm 0.0003$
I think the first one is 2.300 because ...
- 387
4
votes
1
answer
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. ...
- 1,954
3
votes
2
answers
8k
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 ...
- 47
2
votes
1
answer
391
views
Which ions are accounted for in total and net ionic equations?
There are a number of things I don't understand about ionic equations.
First off, when you do net ionic equations, is it correct that you're only focusing on precipitates? The way I understood it, ...
- 175
1
vote
2
answers
401
views
Significant Figures in almost-scientific notation
For a homework assignment on significant digits, I have to find the number of significant digits in the number $0.40 \times 10^3$. I know that in scientific notation, the number of significant digits ...
- 151
0
votes
1
answer
123
views
How to differentiate the notation of a compounds charge and an anions oxidations state?
I have had the case a few times. Being given something of this form:
$$\ce{Cr2O7^2-}$$
How do I know whether the $2-$ is referring to the oxidation of the oxygen anion or the charge of the whole ...
0
votes
2
answers
23k
views
How are lowercase m and uppercase M used in general chemistry courses? [closed]
Where do lowercase m and uppercase M make appearances in general chemistry, and what do they signify?
- 42.3k
-2
votes
1
answer
24k
views
What does the unit M stand for? [closed]
What does $\mathrm{M}$ signify in this pH calculation? To me, it just seems to be a random variable.
For example: $\ce{[H+]} = 1.0\times10^{-7}~\mathrm{M}$
I am not sure what the $\mathrm{M}$ is ...
- 435
34
votes
3
answers
3k
views
Proper typography of "NOx"
I am a journal typesetter, and recently I came to a problem that I'm not sure I know to solve. The question is how to properly typeset the "NOx" abbreviation for nitrogen oxides. Which is ...
- 443
28
votes
2
answers
2k
views
What does this lambda–sigma notation mean?
I am currently reading the CRC Handbook of Phosphorus-31 Nuclear Magnetic Resonance Data by John C. Tebby (CRC Press, 1991) and on several figures (ex. pages 9 to 14) there is a caption that reads ...
- 1,771
24
votes
3
answers
18k
views
What does the circle inscribed in a benzene ring represent?
I have seen benzene being depicted in two different ways:
For the right-hand structure, does the inscribed circle represent the movement of double bonds or electrons?
- 427
24
votes
3
answers
7k
views
Why is the minus sign (-) not allowed in reaction equations?
Recently in my chemistry class, the teacher told us that while writing "half equations" (such as a sodium atom losing one electron to form a sodium ion) we were not to use a simple minus sign. We were ...
- 341
18
votes
3
answers
3k
views
What is the formally correct notation of t-Bu, i-Pr, p-NO2, n-Bu, a-HCl, etc.?
In chemical notation, can I safely assume that the notation of
a single lower-case latin character
followed by a hyphen
followed by an Element upper-case latin character (and possibly more characters)...
- 3,316
14
votes
1
answer
4k
views
For a benzene shown in a skeletal structure, what does a substituent to the center of the ring mean? [duplicate]
I have seen diagrams with both the substituents attached to the benzene ring by the edges and other occasions directly to the delocalized ring. What does signify?
- 313
13
votes
3
answers
3k
views
What does a comma signify in inorganic chemistry?
$\ce{(Ca{,}Co)CO3}$
I have never ever seen this before. What does this mean exactly?
- 147
12
votes
1
answer
6k
views
How are point group character tables typeset correctly?
I want to know how to typeset character tables of point groups correctly. Consider the following two extremes using the $C_{\text{2v}}$ (or is it $\text{C}_{\text{2v}}$?) point group as an example.
...
- 10.9k
12
votes
1
answer
9k
views
What are SN1ʹ and SN2ʹ reactions?
I went through the problems 119 and 120 from chapter 4 Reaction mechanism of Singh's Conceptual problems in organic chemistry [1, p. 190] targeting nucleophilic substitution reactions for 3-bromo-3-...
- 201
11
votes
1
answer
2k
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?...
- 127
11
votes
1
answer
1k
views
What would be SMILES notation for a compound with delocalized bonding?
For example, the cyclopentadienyl rings in ferrocene $\ce{Fe(}\eta^5 \ce{-C5H5)2}$ are often drawn with delocalized electron circles in them instead of explicit pi bonds.
The Wikipedia article for ...
11
votes
1
answer
11k
views
What are the correct equilibrium arrows?
I was recently subject to some atrocious teaching. One of the gems that found me was the equilibrium arrow usage. I am accustomed to write $\ce{<=>}$. Yet, the entire class had to use ⇆ ...
- 331
10
votes
2
answers
2k
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.
...
- 109
9
votes
1
answer
323
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 ...
- 3,316
8
votes
2
answers
2k
views
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 ...
- 91
7
votes
2
answers
2k
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 ...
- 6,262
7
votes
3
answers
9k
views
Confused by notation of atomic number Z and mass number A on periodic table of elements
I'm totally confused by the different conventions and when to use what. In the Periodic Table I see
$$\ce{^{6}_{12}C}$$
However, in books when talking about isotopes I see
$$\ce{^{12}_{6}C}$$
I ...
- 181
5
votes
2
answers
1k
views
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?
- 188
5
votes
1
answer
526
views
What is this SMILES notation: C[Si](C)C |^1:1|
When converting InCHI to canonical SMILES using Indigo, I will occasionally get an output SMILES string like this:
C[Si](C)C |^1:1|
What does the "|^1:1|" part ...
- 153
4
votes
1
answer
365
views
Molecular orbitals symmetry - states notation
I'm reading some papers and I'm repeatedly seeing the following notation of system states:
Could you, please, explain to me the meaning of it?
E.g. the state $B^2 \Sigma_u^+$ - I'm aware, that $\...
- 1,267