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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Comparison of oxygen and carbon-12 as standards for mass

While studying about the standards of atomic and molecular mass, I have learnt that while initially hydrogen was used as a standard of mass (its mass taken as unity), according to my book, oxygen was ...
Smarika Singh's user avatar
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Hydrogen–deuterium exchange in 1,4-benzoquinone

Problem Find number of deuterium exchanges in the following compound. Solution Question I have been taught that hydrogen attached to the carbon which is directly or indirectly in conjugation with ...
Haider's user avatar
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Is a hydrogen atom 'locked' to a given oxygen atom in ice?

Ice, Hydrogen bond, and Ice rules Wikipedia articles seem to imply that the covalently bonded hydrogen atoms are fixed to their given oxygen atom and do not change positions as long as the ice remains ...
ericnutsch's user avatar
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Cesium Chloride Density Gradient Centrifugation and Isotopes

In Cesium Chloride Density Gradient Centrifugation, as used by Meselson and Stahl, Cesium ions can be seen as strongly affected by centrifugation, so much so that they can overcome their ionic bonds ...
Young Jun Lee's user avatar
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The isotopic effect in chemical kinetics

I conducted a chemical experiment (degree in chemical engineering) to understand the isotopic effect in chemical kinetics. In the experiment, I reacted isopropanol and D-isopropanol (D stands for ...
Guy Weizman's user avatar
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180 views

Hydrogen Isotopes and Bronsted Lowry Acid

a Bronsted Lowry Acid is defined as an acid that donates a proton. However it's actually a Hydrogen Ion, since hydrogen only has 1 proton and 1 electron, a positive Hydrogen Ion would have no electron ...
Arno's user avatar
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Stability of beryllium isotopes

I have been reading about isotopes and their abundance on Wikipedia. It states that lithium has 2 stable isotopes, beryllium has 1 stable isotope (monoisotopic and mononuclidic) and boron has 2 stable ...
Proscionexium's user avatar
3 votes
2 answers
222 views

NMR and dienes to isolate certain isotopes?

I am looking to achieve isotope separation using transition states. In the rxn of dienes with halogens, based on the temperature, the dienes can create a thermodynamic product or a kinetic product. ...
Young Jun Lee's user avatar
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1 answer
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Is CD4 an alkane?

Can $\ce{CD4}$ or $\ce{CT4}$ be considered an alkane? I know that an alkane is $\ce{C_nH_p}$ where $p = 2n + 2$. An alkane is considered a "hydro"carbon, i.e., a compound containing purely ...
CHEMUMAN's user avatar
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1 answer
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Electron affinity of isotopes anomaly

According to the Wikipedia article the electron affinity of $\ce{^{2}H}$ is higher than the electron affinity of $\ce{^{1}H}$ however the electron affinity of $\ce{^{18}O}$ is lower than $\ce{^{16}O}$....
Volpina's user avatar
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Masses of atoms and molecules [duplicate]

This is my understanding so far: Average atomic mass is the mass of an element considering isotopes and is measured in atomic mass units. However relative atomic mass is the average mass of an atom ( ...
Quin Gardiner Bax's user avatar
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Can one calculate the polarizability of Xe isotopes using Gaussian 09 and the 3-21G basis?

While trying to understand this paper, I read the following method for calculating the polarizability of different Xe isotopes: Quantum chemical calculation of the exact polarizability of each xenon ...
Ryan's user avatar
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Can deuterium be separated from heavy water via electrolysis? It is an isotope of hydrogen, so I guess it should act in the same way?

I was wondering if it is possible to separate deuterium from heavy water via electrolysis. Also, is this the way deuterium gas is obtained on an industrial scale, or are there better methods?
Arbor Chetia's user avatar
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Is it possible to estimate how much Plutonium existed during the earth's formation?

Plutonium is a man-made element, but minute quantities of it exist on earth. It's probable the earth had much larger quantities of it during its formation as a planet, but most of it decayed due to ...
user148298's user avatar
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Isotopes \ monoisotopic elements [closed]

I am confused about the definition of isotopes I know that isotopes are atoms of an element with different numbers of neutrons. What I don't understand is that we have monoisotopic elements which are ...
Shadow sparkle 's user avatar
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3 answers
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How are the number of neutrons changed in an atom? [closed]

I'm studying isotopes in high school and I don't understand how it works. From my understanding, when neutrons are added or removed, an isotope is created. To calculate the number of neutrons, the ...
user128108's user avatar
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Can the word "iso" be used if the quantities are zero in number?

Both $\ce{H+}$ and $\ce{He^2+}$ ions have zero electrons. So can we call them isoelectronic species? And if two species have a difference in the number of protons and neutrons equal to zero, can we ...
Nipun Kulshreshtha's user avatar
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Determining the average relative mass of an element from the percentage of isotopes

Suppose we have an element $\ce{A}$. Its relative mass is $16$ and it has three isotopes: $\ce{^16A}$ ,$\ce{^17A}$ and $\ce{^18A}$. The available percentage of $\ce{^17A}$ is $0.037\,\%$. What is the ...
Sayem Rahman's user avatar
11 votes
1 answer
617 views

Is there oxygen isotope exchange between dissolved CO2 and H2O?

If you had a sample containing an elevated concentration of $\ce{H2^{18}O}$, and bubbled $\ce{C^{16}O2}$ through it, would some of the oxygen-18 isotope be transferred from water to carbon dioxide? I ...
ericnutsch's user avatar
4 votes
0 answers
91 views

Mapping of half-life decay for all elements/isotopes

Is there an open resource that helps illustrate all paths of decay for all isotopes (e.g. $\ce{^{99}Mo}$ decaying to $\ce{^\mathrm{99m}Tc})?$ I know the result state/transition map would be massive, ...
VenomFangs's user avatar
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Bond frequency vs Bond Strength in Kinetic Isotope Effect

I am confused by the following: in Ansyln's Modern Physical Organic Chemistry, a higher vibrational frequency defines a stronger bond due to the deeper/sharper potential well (page 76). However, the ...
Railgun's user avatar
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6 votes
1 answer
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Why is Gallium-69 stable, Gallium-70 unstable and Gallium-71 stable again?

Why is gallium 70 suddenly unstable, whereas it becomes stable again when you add another neutron? Shouldn't isotopes become unstable when there are either too few or too many neutrons? Why is gallium ...
iwab's user avatar
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8 votes
1 answer
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Are double spike isotopic standards suitable for quantification by isotope dilution mass spectrometry?

I would like to apply isotope dilution mass spectrometry (IDMS)* to quantify lead at trace levels. A good spike solution for the process would be the NIST SRM 991 which is an enriched material of ...
Cris's user avatar
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Mass spec mass calculation difference

This is not a homework question, but for research. I am performing mass spec on serum metabolites using Thermo Q Exactive PLUS with a HESI source which was set to a spray voltage of -2.7kV under ...
William Wong's user avatar
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Neutron–proton ratio and isotope stability

I have studied that most of the isotopes (not all of them!) with a neutron–proton ratio of $\ge 1.5$ are unstable; but it is obvious that this is not true in some cases like carbon-14 or technetium-99....
Peshawa_Aziz's user avatar
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How is this Clemmensen Reduction taking place? [closed]

How did that isotopically labelled Carbon migrate? I know that an carbanion is formed, but I am not able to conclude the final product. Please Help
Sharad Kothari's user avatar
2 votes
1 answer
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g-tensor and hyperfine tensor for nitroxide spin label with 15N

Does anyone know where I can find numerical data for the $g$ tensor and hyperfine tensor for a nitroxide spin label where the nitrogen-14 atom has been replaced by a nitrogen-15 atom? I'm really ...
Ben's user avatar
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Does the Atomic Mass listed for each element on the periodic table reflect the relative abundances of their isotopes on Earth? Or in the Universe? [duplicate]

Somehow, I cannot find a site or book or paper explaining exactly how the average atomic masses for the elements on the periodic table are weighted.... I posted a question either here or on Physics S....
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Where do the electrons for which RTG's use for the Seeback effect come from?

I know that RTG's use Radioactive Isotope that emit Alpha particles generally (ie. NASA uses Pu 238), I also know that these Alpha particles are consiting of 2 Protons and 2 Neutrons, since the RTG ...
WIlliam Wang's user avatar
4 votes
3 answers
322 views

If all molecules have basically the same KE at a given temperature, why do lighter isotopes evaporate more readily?

One of the proxies used for paleoclimate is the ratio of oxygen-18 to oxygen-16 in ice cores and in sedimentary rocks. The idea is that water molecules with oxygen-18 generally evaporate less readily ...
Michael Seifert's user avatar
1 vote
1 answer
152 views

Can the enrichment of Uranium be done via manipulating the boiling/melting point difference between differing isotopes of the same element?

I have a Physics question for which I could not find the answer on the Internet, so I would like to see if y'all know the answer to it. I have found that heavy water will have a different boiling ...
Young Jun Lee's user avatar
3 votes
2 answers
304 views

Long-lived, non-lethal radioisotope for fiction [closed]

I'm writing something where the characters are looking for someone among a large set of people. They don't know who this person is and they don't know what they're looking for, so their best bet is to ...
Nicola's user avatar
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3 votes
1 answer
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What is the heaviest possible water using oxygen and hydrogen isotopes, and what might it's physical properties be? [closed]

After a cursory internet search, it appears to me that Hydrogen-3 (a part of Tritiated Water) is the heaviest stable* hydrogen isotope. Oxygen-21 is the heaviest isotope of Oxygen with a half-life of ...
Jay Glenn's user avatar
3 votes
2 answers
117 views

Biological activity of the isotopes of the same element

I have a question regarding biological activity of different isotopes of the same elements, notably $\ce{^206Pb}$ and $\ce{^208Pb}$. Lead is known to be toxic, such that it can replace calcium from ...
hmm...'s user avatar
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1 answer
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What does radioactive decay look like?

Some element isotopes have half-lives that are as short as a couple minutes to an hour. Does that mean you can watch it (or catch it on video) turn into 2 different elements? What would something like ...
Axis Omega's user avatar
4 votes
0 answers
36 views

Normalising Kinetic Isotope Effect Per Deuterium Atom

I've synthesised a protic and deuterated version of a specific molecule where there are two deuterium atoms in the latter. I then go about and measure the kinetic isotope effect (KIE) for a reaction ...
Hazinga's user avatar
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2 votes
2 answers
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How do we know the natural abundance of isotopes on Earth?

Without knowing the Average Atomic Mass or the percent abundance, how do we know that Protium is the most prevalent hydrogen isotope? What methods did scientists use to come to this conclusion? How ...
Gianna's user avatar
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isotopic composition database for carbon isotopes

I am seeking an isotopic composition database for carbon isotopes, since I would like to make a figure showing the different isotopic compositions of different materials. The best woudl be if the ...
Zorg's user avatar
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2 answers
71 views

Probability of forming dihydrogen with molecular weight 3 [closed]

During a lecture, my professor told us that the probability $P$ to form a hydrogen molecule $\ce{H2}$ with mass number 3 could be calculated out of the abundances, $\gamma$, of the isotopes of this ...
Vicky's user avatar
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3 votes
1 answer
278 views

Who figured out that different isotopes have different numbers of neutrons?

I reasearched about the history of the discovery of neutrons and couldn't find who found out that isotopes are a change in the number of neutrons. Can you please tell me who it was that made this ...
Amruth Arunkumar's user avatar
3 votes
1 answer
104 views

Why burn methane to CO2 for isotopic analyis?

I am wondering why mathane is burned to CO$_2$ for isotopic analysis, e.g with a mass spec? I have looked into several text books, they all describe how to do it but not why. Is it because of a ...
Zorg's user avatar
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-1 votes
1 answer
512 views

The unit of relative atomic mass [closed]

The mass of Carbon-12 atom is 12.0000000 a.m.u. For relative isotopic mass, e.g. Mg-24 atom is 24 compare with the c-12 as standard. However, why is it unitless? Shouldn't it be 24 a.m.u.?
Jessica 's user avatar
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How much D2O is in Vienna Standard Mean Ocean Water?

I'm curious how much $\ce{D2O}$ (heavy water) is in Vienna Standard Mean Ocean Water. I am interested in $\ce{D2O}$ molecules and not $\ce{HDO}$/$\ce{D+}$/ $\ce{DH2O+}$/$\ce{D2HO+}$/$\ce{D3O+}$ or any ...
darsie's user avatar
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6 votes
1 answer
227 views

Behavior of Natural Abundance and Mass Spec Ratios

The presence of sulfur in a mass spec is 96% and 4%. I believe this to be because the natural occurrence of sulfur isotopes are within these proportions. However, chlorine behaves in a 66%/33% ratio ...
Moobius Strip's user avatar
-1 votes
1 answer
160 views

An expression for equilibrium constant of isotope reaction

Consider the isotope exchange reaction: $$\ce{C ^{16}O + 1/2 ^{18}O {}^{18}O <=> C^{18}O + 1/2 ^{16}O^{16}O}$$ The equilibrium constant for the reaction is: $$K=\frac{\prod (a_i)^{n_i}_{products}...
2020's user avatar
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1 vote
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Why isn't carbon-14 included in CIAAW list of isotopic abundances? [closed]

According to Wikipedia, standard atomic weight is based on the published isotopic abundances of CIAAW: The standard atomic weight $(A_\mathrm{r},$ standard) of a chemical element is the weighted ...
Nathan Long's user avatar
1 vote
0 answers
320 views

Do isotopes have the same ionization energy? [duplicate]

When learning about isotopes and IE in High School this question have come to my mind recently. I have asked the teacher, she told me that she read articles about it however could not come to a ...
Cfem's user avatar
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4 votes
1 answer
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Stronger ESI signal for deuterated substances

I observe a constant phenomenon in my ESI measurements, which indicates that deuterated substances give a stronger signal than the same substance in non-deuterated form. Unfortunately I can't make any ...
Sam's user avatar
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Why do isotopes have different chemical reaction rates? [duplicate]

Isotopes of a given element differ in the rates at which they undergo chemical reaction. Why is this so? The only explanation I could think of is that the gravitational force on the electrons ...
Michael Faraday's user avatar
1 vote
1 answer
165 views

Is enthalpy affected by isotopes?

Enthalpy is a sum of $U$ and $PV$, and I thought that for different isotopes, internal energy values may differ. Is it true? There are three stable isotopes of $\textrm{Mg}$, mass number 24, 25, and ...
coxehj4142's user avatar