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Questions tagged [isotope]

This tag should only be applied where the effects are specifically related to variance in mass number with the same atomic number (existence of isotopes). Examples include: radioactivity and other nuclear properties, kinetic effects, specific relevance to spectroscopy (e.g., NMR, IR), isotope separation, isotopic analysis.

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36 views

Classic/killer/easy application for the deuterium kinetic isotope effect?

I'm a physicist. While visiting someone's o-chem class I learned about the existence of the deuterium kinetic isotope effect. This seems like an extremely sweet example of zero-point energy, and I ...
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Does the distillation of alcohol cause the fractioning of isotopes and carbon-12 enrichment?

In water, distillation causes fractioning of the $\ce{^{18}O}/\ce{^{16}O}$ oxygen isotopes (Wikipedia). Does something similar happen to the $\ce{^{13}C}/\ce{^{12}C}$ and possibly $\ce{^{14}C}$ ...
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What is mass-independent isotope separation/fractionation?

How can any separation/fractionation of isotopes be mass-independent, if the only difference between two isotopes is mass? The only clue(s) on Wikipedia mention molecular symmetry, 'forbidden' spin-...
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Why do foraminifera use less magnesium in their shells when the water is cold?

When scientists study ancient seabed cores, they say they can judge the temperature of the water in the past by analyzing the magnesium to calcium ratio in foraminifera shells (both in the form of ...
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3answers
686 views

Why are isotopes an issue in reading mass spectra?

It is my understanding that the isotope distribution for carbon and hydrogen, for example, are skewed heavily toward one species, i.e., one isotope accounts for ~99% of the abundance of the element in ...
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3answers
96 views

Strontium-89 vs strontium-90

Why is radioactive strontium-89 is considered medically useful for bones (along with other benefits) whereas strontium-90 (also being radioactive) is harmful for human body? How does the addition of ...
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1answer
153 views

What makes an isotope stable? [closed]

I have heard many times that when there is the “right balance” of protons and neutrons the atom will be stable, and therefore it will decay to achieve this stability. But what about this supposed ...
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1answer
67 views

Removing PTFE marks on glass bottles after using magnetic stir bars

I am using magnetic stir bars to agitate solutions for 4 weeks at a time. I have noticed at the bottom of the glass bottles that white marks have accumulated where the stir bar spins. Even with ...
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3answers
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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 ...
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28 views

Isotope labeled experiment analysis

I'm analyzing a dataset generated with LC-MS from cells that were fed $\ce{^13C}$-Glucose. There are 3 groups in total each with a different media conditions. My goal is to identify differences ...
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1answer
35 views

Number of stable molecules of artificial molecule XY4 [closed]

Suppose element X has $5$ stable isotopes, and element Y has $6$ stable isotopes. Find the number of natural molecules, knowing that an X has a charge of $+4$ and Y has a charge of $-1$. What I tried ...
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35 views

How to define the reduced mass for estimating Kinetic Isotope Effects

I am trying to think about radical reactions using zero-point energies (from the harmonic oscillator model). I have read that substitution of a bond with isotopes can alter the rate of a reaction. ...
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1answer
63 views

Must a sample of a deuterated compound be isotopically pure for kinetic isotope experiments?

I'm trying to do a project on the primary kinetic isotope effect on the dehydroxylation of $\alpha-FeOOH$, goethite. The goethite consists of edge-sharing double octahedra of 3 oxyanions and 3 ...
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3answers
70 views

Isotopes of Elements

When we talk about the substance $\ce{H2O}$ with a molar mass of $\pu{18.0 g/mol}$, what hydrogen and oxygen isotopes are present in the $\ce{H2O}$ molecules? In other words, what isotopes do the ...
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4answers
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Is an isobar the same as an isotope?

I am a little bit confused about what an isobar is. Its online definition is that it's an element with the same number of neutrons but a different number of protons from an element $\ce{X}$. To me, ...
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2answers
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Francium has isotopes so how can its atomic mass be a whole number?

Why do francium, radon, radium, and actinium have whole numbers for average atomic mass even though they have isotopes? But then elements like beryllium, fluorine, and sodium are listed as having no ...
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1answer
50 views

Can I expect 18O-hydroxide when adding slight amount of NaOH-16O to 18O-water?

In adding $\ce{^{16}O}$-sodium hydroxide to $\ce{^{18}O}$-water to get a $0.25\pu M$ solution, is the hydroxide in form of $\ce{^{16}O}$-hydroxide or $\ce{^{18}O}$-hydroxide? is there an oxygen ...
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1answer
927 views

What is [U-14C]-glucose?

In Helen Tweeddale's article,[1] they labelled metabolites of E. coli with [U-$^{14}$C]glucose. What sort of glucose is it? I understand they used isotope 14, which is radioactive but what does the U ...
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1answer
72 views

Fluorine and fossils

They are now assisted by chemists who are able to fix dates through the analysis of pollen, radioactive carbon, and fluorine found in connection with fossils.. Here the text is talking about basic ...
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1answer
605 views

Why is the standard atomic weight of chlorine not a whole number? [duplicate]

Why is the standard atomic weight of chlorine, 35.5, not a whole number? Like for example, it could be exactly 35 or exactly 36. Please show the solution of formulae on how u reach to 35.5) with some ...
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2answers
82 views

Atomic weight = expected weight?

The atomic weight of an element, is it accurate to say that another way to think of it is the expected value of that element's weight if we were to sample one at random from the environment? Are man-...
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1answer
604 views

Which element has the highest binding energy per nucleon

The graph of binding energy per nucleon (Hyperphysics) seems to peak at Iron-56. However, Wikipedia says that Nickel-62 has the highest binding energy per nucleon of any known nuclide (8.7945 MeV). ...
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1answer
63 views

Making sulfate from elemental sulfur [closed]

I have $\approx\pu{2 g}$ of elemental sulfur that I need to convert to dissolved sulfate in DI water. What's the easiest lab chemistry that will get me there?
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1answer
53 views

Is there a blanket term for all variants (both nuclides and ions) of a chemical element?

I'm hoping to catalogue the various nuclides and oxidation states of an element but can't find a single term that describes them all, save for "chemical element variations". Is there a specific term ...
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1answer
750 views

How is phosphorus-32 produced?

I'm doing an assignment where I have to research a radioisotope of my choice. I decided to do phosphorus-32 and my assignment requires me to explain how the isotope is made. There is very minimal ...
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1answer
145 views

Is water with oxygen-17 safe to drink? [closed]

Is it safe to drink and what else can it be used for?
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2answers
122 views

Does CHT=CHT have a geometric isomerism because of tritium atoms?

Is the radioisotope of hydrogen considered as a new atom? Can you detect it with an H NMR?
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0answers
34 views

Carbon 14 in organic chemistry [duplicate]

A small amount of natural carbon is $\ce{^{14}C}$. This is radioactive and decays to $\ce{^{14}N}$. This is exploited in radiocarbon dating. This $\ce{^{14}C}$ is taken up by living organisms. I ...
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2answers
312 views

Do light and heavy water form an azeotrope?

(Interested in the general principle too, not just for water and its variants, but with particular emphasis on it.) When you distill a weak ethanol-in-water solution, you get a condensate that's ...
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1answer
336 views

Isotopic mass to density

I want to figure out/calculate the density ($\pu{g/cm3}$) of the various isotopes, here $\ce{^109Ag}$. I know it's isotopic mass is $\approx109$ and calculated the number of particles/gram. But I ...
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2answers
2k views

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?

The mass spectrum in Bromine, with the molecules $\ce{^{158}Br2+}$, $\ce{^{160}Br2+}$ and $\ce{^{162}Br2+}$: As you can see, the $\ce{^{160}Br2+}$ is almost double in intensity compared to the $\ce{^{...
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1answer
2k views

How many peaks of HCl are found in a mass spectrum?

In a mass spectrometer some hydrogen chloride molecules will split into atoms. Chlorine has two isotopes. The hydrogen involved here is the isotope $\ce{^1_1H}$ only. How many peaks does a mass ...
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1answer
420 views

What is the difference between a time of flight mass spectrometer and a spectrometer that uses a magnetic field?

Traditional mass spectrometers used electromagnets to deflect isotopes of different masses which allowed only a certain isotope to reach the detector. But how is the TOF MS different besides the fact ...
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1answer
401 views

How many isotopologues of water are there?

If ordinary water molecules can contain any of the three hydrogen isotopes, $\ce{^1H}$, $\ce{^2H}$, $\ce{^3H}$, and any of the three oxygen isotopes, $\ce{^{16}O}$, $\ce{^{17}O}$, $\ce{^{18}O}$, how ...
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1answer
3k views

Why do higher-mass isotopes have higher melting and boiling points than lower-mass isotopes?

Different isotopes of the same element have the same number of electrons, so the nature of bonding between different isotopes of the same element should be the same, yet their melting points and ...
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1answer
595 views

Freezing point of oxygen-18 water

The freezing points of heavy water (3.8 °C) and tritiated water (4.49 °C) both seem to be well-known. I can't find anywhere that gives the freezing points of $\ce{H2^18O}$, $\ce{D2^18O}$, or $\ce{T2^...
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2answers
1k views

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

Three isotopes of an element have mass numbers $(M)$, $(M+1)$ and $(M+2)$. If the mean mass number is $(M+0.5)$, then the ratio of the amounts of the three isotopes is? Let amount of $(M)$, $(M+1)$, ...
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2answers
61 views

Where can I find ranges of isotope abundances?

I'd like to know how much stable isotopes like $\ce{^{13}C}$, $\ce{^2H}$, $\ce{^{17}O}$ and $\ce{^{18}O}$ deviate from their natural abundances in the earth's crust among all possible compounds we may ...
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1answer
201 views

Why would a reaction favor one isotope over another?

In my instrumentation class last semester, we were asked to read a short paper. The paper described a technique for determining whether dinosaurs were cold-blooded or warm-blooded based on the amount ...
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1answer
271 views

Heavy-oxygen water production

It is easy to find information about heavy-hydrogen water production, but not about heavy-oxygen water. How is heavy-oxygen water commercially produced (for both heavier isotopes)?
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2answers
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Can isotopes of a given element be represented by different symbols?

Can isotopes of any given element be represented using a completely different chemical symbol? What's the IUPAC's take on this? Sure, ordinarily you would add the isotope's mass as a superscript to ...
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1k views

Are stronger bonds always shorter?

This question relates to a few earlier questions I have seen on the site (particularly this one about the bond strength of heavier isotopes). Does a bond necessarily have to be shorter to be stronger? ...
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409 views

Best Radioactive Isotopes for Energy Generation [closed]

First off, this is research for a video game storyline, I like to be thorough. -- I am looking for the most efficient method of nuclear power generation which: Can survive for hundreds/thousands of ...
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1answer
306 views

Why are isotopically pure diamonds 50% more thermally conductive than other diamonds?

A laboratory grown type-IIa diamond (no nitrogen defects) has a lambda of $\pu{1800-2200 W/mK}$, but an isotopically pure diamond of $\ce{^{12}C}$ can have up to $\pu{3320 W/mK}$. Why are $\ce{^{12}C}...
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1answer
684 views

Meaning of m2 in the symbol for an isotope of an element

What does the notation $^{197\mathrm{m}2}\ce{Pb}$ mean? Specifically, the '$\mathrm{m}$2' part. I've found this and it appears to have something to do with charge distribution. The original notation ...
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1answer
404 views

If the half-life of an isotope exceeds the age of the Universe, then how is it measured?

According to this Wikipedia article, the half-life of Bismuth-209 is 19 billion billion years, which exceeds the age of the Universe by factor on the order of a billion. How is the half-life of an ...
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1answer
3k views

Carbon-13 NMR for chloroform

I am slightly confused by what the spectrum would show for carbon-13 NMR of $\ce{CHCl3}$. My initial guess would be that the peak would be split by coupling to both the proton and the 3 chlorines, as ...
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2answers
137 views

Burning different isotope combinations of hydrogen and oxygen, how much does the energy vary?

In this comment I suggested that there would be a (very) small difference in energy released from burning a stoichiometric mixture of hydrogen and oxygen, depending on the isotopes, due to a slight ...
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1answer
536 views

How to specify a different isotope in the ORCA quantum chemistry program?

I would like to carry out a calculation using deuterium instead of hydrogen. I tried the following ORCA input file: ...
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1answer
766 views

Dipole Moment of Normal Water vs Heavy Water

The question is in the title itself. My guess: Higher for Normal water. My Reasoning: Internet told me Deuterium is more electronegative than Protium. So, there should be less difference between ...