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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48 views

Probability of forming dihydrogen with molecular weight 3

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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176 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
61 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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47 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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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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1answer
132 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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91 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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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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0answers
83 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
167 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
57 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
41 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
52 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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23 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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36 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
14 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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61 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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269 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
145 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
441 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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50 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
59 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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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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714 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
124 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
302 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
102 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
5k 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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31 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
46 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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92 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
93 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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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
3k views

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
59 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
2k 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
74 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
1k 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
92 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
2k 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
88 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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1k 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
185 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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169 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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36 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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3answers
6k views

Can you make deuterium-depleted water through a freezing method?

Deuterium-depleted water (DDW) is sold commercially by some companies. It is apparently manufactured by fractional distillation, which leverages differences in boiling points of heavy and light water. ...