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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117 views

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....
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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
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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find numerical data for the $g$ tensor and hyperfine tensor for a nitroxide spin label where the nitrogen-14 atom has been replaced by a nitrogen-15 atom?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 ...
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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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42 views

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 ...
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3answers
102 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 ...
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55 views

How would one separate a mixture of isotopes (different nuclear spins) at temperatures near 0 Kelvin?

Suppose we have two isotopes of the same element. For example, isotope A could have a nuclear spin I = 0, isotope B could have nuclear spin I = 3/2. Let us say we have a compound where this element is ...
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1answer
73 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 ...
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2answers
296 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 ...
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68 views

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 ...
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100 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 ...
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70 views

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 ...
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24 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 ...
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2answers
166 views

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 ...
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25 views

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 ...
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2answers
58 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 ...
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1answer
223 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 ...
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1answer
72 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 ...
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1answer
160 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.?
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80 views

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 ...
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147 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 ...
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1answer
110 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}...
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66 views

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 ...
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254 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 ...
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1answer
173 views

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 ...
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1answer
178 views

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 ...
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1answer
51 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 ...
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1answer
77 views

Type of structural isomerism

What is the type of structural isomerism in which isotopes move around? Examples $\ce{CH2D-NH2}$ and $\ce{CH3-NHD}$ $\ce{CH2D-NH-CH3}$ and $\ce{CH3-ND-CH3}$ $\ce{CH2D-NH-CH2CH3}$ and $\ce{CH3-NH-CHD-...
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3answers
2k views

What is the relationship between entropy and heat capacity?

The molar heat capacity of hydrogen gas and deuterium gas are nearly the same, $\pu{28.8 J K-1 mol-1}$ and $\pu{29.2 J K-1 mol-1}$, respectively, but the absolute entropy of deuterium ($\pu{145.0 J K-...
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27 views

Do radioisotopes emitted particles influence their chemistry? [duplicate]

Supposedly, a isotopes have the same chemistry, i.e. how they bond to other atoms. Is this true for radioisotopes? I can imagine a nucleus emitting particles that interact with existing bonds in its ...
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53 views

Ionization and bond energy of isotope [closed]

Is there a database with the direct values, or the ingredients to calculate them, for ionization and bond energies of isotopes (i.e. $^{17}O_2$). If I understand it right, ionization energy can be ...
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1answer
17 views

Effect of pH on sulphur isotope variation on a landscape

I recently ran a forest regression model, this model showed me that increasing soil pH increases sulphur isotope variation across the landscape. I am not how this is possible and if it makes sense
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142 views

Finding Symmetry number of a molecule [closed]

An isotopic variant of the molecule SF$_6$ is S$^{19}$F$_4^{18}$F$_2$, with the two $^{18}$F nuclei oriented axially, so that the $^{18}$F-S-$^{18}$F angle is 180°and the four $^{19}$F nuclei form a ...
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379 views

Do isotopic groups cause optical activity?

I understood the simplified reason for optical activity of a compound based on the difference in the angular velocities of counter-rotating circularly polarized light. The difference is due to the ...
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2answers
206 views

Kinetics of converting a water + heavy water mixture to HDO

Imagine an initial 50%-50% mixture of normal ($\rm H_2 \rm O$) and heavy water ($\rm D_2 \rm O$). I think, simply mixing them, the result will exponentially converge to an equilibric state, where ...
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1answer
767 views

Characteristics of Isotopes [closed]

I'm currently applying information theory to physics, and have begun considering the nature of isotopes, and in particular, how much information is contributed to the properties of an element by its ...
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52 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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1answer
69 views

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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21 views

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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31 views

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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735 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
170 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
353 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
138 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
7k 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 ...
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34 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
104 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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141 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
128 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 ...