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85 votes
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Is it true that heavy water is not blue?

Based on your description, I may have found the article you originally saw, or at least one very similar. Researchers from Dartmouth College published a paper$\mathrm{^1}$ in which they report, among ...
airhuff's user avatar
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71 votes

Is it true that heavy water is not blue?

This does seem to be the case. I don't have images of the different types of water, but I did find this overlaid IR-visible spectrum of water and heavy water: As you stated, the presence of deuterium ...
Tyberius's user avatar
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34 votes
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Is an isobar the same as an isotope?

Not quite, an isotope has same number of protons ($ A- N = Z = \mathrm{constant}$), but a different number of neutrons ($\mathrm N$ varies; e.g. $\ce{^3_\color{red}{1}H}$ and $\ce{^2_\color{red}{1}H}$,...
A.K.'s user avatar
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27 votes
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Why is the probability for the signal at 160 in the bromine mass spectrum twice as high as for the signals at 158 and 162?

All possible arrangements of $\ce{Br2}$ molecule: $\displaystyle 79 + 79 = 158$ $\displaystyle \color{red}{79 + 81} = 160$ $\displaystyle \color{red}{81 + 79} = 160$ $\displaystyle 81 + 81 = 162$ ...
Stanislav Bashkyrtsev's user avatar
22 votes
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Can isotopes of a given element be represented by different symbols?

IR-3.3.1 Isotopes of an element The isotopes of an element all bear the same name (but see Section IR-3.3.2) and are designated by mass numbers (see Section IR-3.2). For example, the atom of atomic ...
Berry Holmes's user avatar
  • 4,144
18 votes

Francium has isotopes so how can its atomic mass be a whole number?

For elements with no stable isotope (i.e. francium, radium, and actinium), the atomic mass is chosen to be that of the longest lived isotope. More generally, the masses for stable elements are ...
PJ R's user avatar
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15 votes
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Are stronger bonds always shorter?

This is an interesting question and depending on how you define bond strength the answer is different. Let us for simplicity consider only diatomic molecules and let us assume that the electronic ...
Paul's user avatar
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14 votes
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Is it possible to find the ratio of isotopes only given the mean mass number?

You have two equations and 3 unknowns, so you can't solve it with just that. Say a, b, c are the fractions (as a decimal) of each isotope... $$ a(x) + b(x+1) + c(x+2) = (x+\frac{1}{2}) $$ $$a + b + ...
iammax's user avatar
  • 1,009
13 votes

Is it possible to find the ratio of isotopes only given the mean mass number?

As already stated, the system of equations is underdetermined. But we can get the range of possible solutions. Starting with \begin{equation} xM + y(M+1) + z(M+2) = M + \frac{1}{2} \end{equation} ...
Feodoran's user avatar
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13 votes
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Freezing point of oxygen-18 water

In this paper [1] from 1963, various properties of heavy-oxygen water are measured including the melting point of both $\ce{H2^{18}O}$ and $\ce{D2^{18}O}$. The melting temperatures were measured at: $...
jheindel's user avatar
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13 votes
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Confused by notation of atomic number Z and mass number A on periodic table of elements

Periodic tables of elements (PTEs) are often abused by designers. Books are more trustworthy as long as they are written by scientists. Long story short, the second notation $(\ce{^{12}_{6}C})$ is the ...
andselisk's user avatar
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12 votes

Do isotopic groups cause optical activity?

From a 2007 paper:: Here we show that instrumental advances in Raman optical activity, combined with quantum chemical computations, make it possible to determine the absolute configuration of (R)-[$...
Curt F.'s user avatar
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12 votes
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Is there oxygen isotope exchange between dissolved CO2 and H2O?

As Todd Minehardt points out, not only can the oxygen be exchanged, but this exchange is applied in aqueous geochemistry. The exchange occurs through the formation of carbonic acid, given in blue ...
Oscar Lanzi's user avatar
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11 votes

Is it true that heavy water is not blue?

If you saw it during the 1990s online era, it might well have been reference links on my old website, from this article on physics misconceptions in grade school. I'd been doing some textbook-...
wbeaty's user avatar
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11 votes
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If the half-life of an isotope exceeds the age of the Universe, then how is it measured?

Well, half-life describes the time after which half of the substance has decayed. This is all probability and statistics. If you look at a single atom you cannot make any prediction when it will ...
DSVA's user avatar
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11 votes
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How to specify a different isotope in the ORCA quantum chemistry program?

ORCA cannot read isotope information from XYZ files -- the OpenBabel specification does not include it and so ORCA doesn't look for it in the geometry file. You need to copy-paste the geometry into ...
hBy2Py's user avatar
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11 votes
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Can an ion isotope exist?

Short answer: Yes. Longer answer: Isotopes are atoms of the same element that have different numbers of neutrons in their nuclei. Everything else about them is the same. The numbers of protons and ...
Ben Norris's user avatar
11 votes

Are stronger bonds always shorter?

I would like to add a few cases featuring A-A type bonds, where bond strength and bond length orders follow quite an anomaly. $\ce{N-N}$ and $\ce{P-P}$ bonds. The lone pairs present on nitrogen atoms ...
Berry Holmes's user avatar
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11 votes
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What is [U-14C]-glucose?

According to the IUPAC organic chemistry nomenclature 2013, section P-83 ISOTOPICALLY LABELED COMPOUNDS, it has to do with uniformly labeled compounds: P-83.5 GENERAL AND UNIFORM LABELING P-...
mykhal's user avatar
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11 votes

Francium has isotopes so how can its atomic mass be a whole number?

For highly radioactive elements that don't occur in large quantities in nature, the mass number listed is the mass number of the most stable isotope. When this is done, the value is often written in ...
Tyberius's user avatar
  • 11.8k
11 votes

Is an isobar the same as an isotope?

I believe the definition you found may have been a little bit misleading. Here is another definition of isobar I found: each of two or more isotopes of different elements, with the same atomic weight. ...
Eli Jones's user avatar
  • 2,020
11 votes

Why are isotopes an issue in reading mass spectra?

Here is the "periodic table for biomolecules" (leaving out hydrogen, please ignore silicon): The pie chart shows the isotope distribution. Of the elements C, N O, P, S and H, sulfur has the highest ...
Karsten's user avatar
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10 votes

Why is there no neutron in protium?

@Jan's put up a nice and crisp, answer. My answer is merely a supplement to that ;) It's because the hydrogen ("protium", if you will) nucleus has no need for neutrons. What's this "need for ...
paracetamol's user avatar
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10 votes
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Meaning of m2 in the symbol for an isotope of an element

As per this Wikipedia page on isotopes: The letter $m$ is sometimes appended after the mass number to indicate a nuclear isomer, a metastable or energetically-excited nuclear state (as opposed to the ...
Todd Minehardt's user avatar
10 votes

Can isotopes of a given element be represented by different symbols?

While it is read like "carbon 12", and "carbon 14", etc. the atomic notation of the nuclides is the other way around, i.e. the mass number precedes the element symbol. Hence it is not $\ce{C^{12}}$, ...
Buttonwood's user avatar
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10 votes

Why is Gallium-69 stable, Gallium-70 unstable and Gallium-71 stable again?

There is the general neutron/proton ratio rule, regarding stability of nuclides, described by the Valley of stability. Additionally, in beta decay context, there are 3 easily remembered rules, based ...
Poutnik's user avatar
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9 votes
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How many isotopologues of water are there?

In an example as small as this, you could hypothetically construct all the cases, or at least enough of them to see that $9$ is incorrect. The only thing you need to change to get the right answer ...
Tyberius's user avatar
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9 votes
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Why is the standard atomic weight of chlorine not a whole number?

The process is explained (for silicon) here: The calculation is exemplified for silicon, whose relative atomic mass is especially important in metrology. Silicon exists in nature as a mixture of ...
Glorfindel's user avatar
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9 votes
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Behavior of Natural Abundance and Mass Spec Ratios

You are probably mixing natural abundance (NA) and relative abundance (RA). In mass spectrometry RA is a more valuable parameter as it can be directly obtained as the $y$-coordinate of a plotted mass ...
andselisk's user avatar
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