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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77
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4answers
17k views

Is it true that heavy water is not blue?

I believe I saw this claim somewhere on the internet a long time ago. Specifically, it was claimed that the difference could be observed by filling one long, straight tube with light water and one ...
41
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4answers
7k views

What is more acidic: D3O+ in D2O or H3O+ in H2O and why?

What is more acidic: $\ce{D3O+}$ in $\ce{D2O}$ or $\ce{H3O+}$ in $\ce{H2O}$ and why? I think it's $\ce{D3O+}$ in $\ce{D2O}$ as I saw somewhere that this property is used in mechanistic studies (...
34
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2answers
16k views

Inductive effect of hydrogen isotopes

Why does the electron-donating inductive effect (+I) of the isotopes of hydrogen decrease in the order $\ce{T} > \ce{D} > \ce{H}$? (where T is Tritium and D is Deuterium) Google has nothing to ...
33
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4answers
6k views

Why are isotopes of hydrogen the only ones with special names?

Why does no other element but hydrogen get special names for its isotopes?
28
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1answer
6k views

How come uranium's relative atomic mass is 238.03 when it only contains isotopes with a mass number of 238 or less?

I have always been led to understand that the mass of an element on the periodic table is the weighted average atomic mass over all naturally occurring isotopes. This seems to make sense with all the ...
23
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3answers
2k 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? ...
21
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1answer
1k views

Are there any known chemical properties of tritium water that make it unusually different from protium water?

I suppose the first question supporting the main question is, has tritium water ever been synthesized in sufficient quantity to test chemical properties? If so, and apart from the obvious radioactive ...
20
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4answers
3k views

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, ...
20
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2answers
5k views

For a given element do heavier isotopes form stronger bonds than lighter isotopes?

I know that $\ce{C-D}$ and $\ce{C-T}$ bonds are stronger than $\ce{C-H}$ bonds, but is this generally true for isotopes of all elements? (By isotopes I mean stable ones with large half lives.)
18
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2answers
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Is the relative natural abundance of isotopes of an element the same everywhere?

Wherever you find potassium, the isotopes are present in a set percentage that exists the same everywhere in nature, but why is that? Does it have something to do with how the element is produced?
16
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3answers
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Is there a simple way to separate deuterium oxide from tap water?

I understand that tap water contains minute amounts of deuterium oxide (heavy water). Is there a simple way to separate, concentrate the $\ce{D2O}$?
15
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1answer
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What is deuterium-depleted water actually used for?

I noted, flipping through the paperback Alfa Aesar catalogue today, that they sell deuterium-depleted water. Under the usage category, they list 'NMR'. I'm trying to work out what specific use this ...
14
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7answers
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Is there a simple field test for heavy water?

Thought experiment Given two glasses of water, how would one detect which glass contains heavy water, and which contains potable water without using complicated laboratory equipment? Something like ...
14
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1answer
10k views

Why atomic masses aren't integers?

Most of the elements have isotopes, so the atomic masses are calculated depending on the percentage of the existing isotopes. That is clear. However, what about elements that have only one isotope (...
13
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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 ...
12
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1answer
2k views

Does hydrogen really have seven isotopes?

I know that there are 3 isotopes of Hydrogen. But according to this website it is showing 7 http://periodictable.com/Properties/A/KnownIsotopes.htmlWebsite
12
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3answers
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Biological Consequences of Asteroid Mining—Death by Isotope?

It's been documented that NASA hope to capture an asteroid in 2025, and have subsequent aims to mine that asteroid. If if this is successful, we would expect other asteroids to be mined in the future. ...
12
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3answers
3k views

On the stability of deuterium

The isotope of hydrogen, tritium, is indeed radioactive resulting in $\ce{^3He}$ through beta decay. But what of the radioactively 'stable' isotope deuterium? Are all deuterium atoms destined to be ...
11
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2answers
1k views

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 ...
11
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3answers
710 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 ...
11
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2answers
522 views

Radical formation via tritium to helium decay

Following on from this question about tritium water, I was wondering whether the decay of tritium to helium-3 has ever been used in organic synthesis. Such a transition would presumably result in no ...
10
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2answers
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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?

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{^{...
10
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2answers
2k 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 $(M)$, $(M+1)$, ...
10
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1answer
829 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^...
10
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1answer
361 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}...
9
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2answers
264 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 ...
9
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2answers
1k views

Where does the molar mass difference between N₂ and CO come from?

The molar masses of $\ce{N2}$ is 28.0134 g/mol, for $\ce{CO}$ it's 28.0101 g/mol (WolframAlpha computation). Of course, they do have the same mass in atomic units (28). My question is, where does ...
9
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2answers
402 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 ...
9
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2answers
664 views

Does the natural abundance of radioactive elements change?

Given that the half-lives differ between isotopes of a particular radioactive element, wouldn't the natural abundance change (fairly rapidly)? For example, if we isolated a bunch of thorium, wouldn't ...
9
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1answer
1k 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 ...
9
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1answer
207 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 ...
8
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2answers
2k views

Is real water made up of heavy water and light water?

I need to know, is real water made up of heavy water which is formed with deuterium, and light water which is water by protium? We know that hydrogen has three major isotopes, including protium and ...
8
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3answers
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Are radioactive isotopes of silver dangerous?

I know we all think of things like uranium as being radioactive in the nasty radiation poisoning sort of way. But do elements like silver have similar effects in their radioactive isotopes? I'm an ...
8
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2answers
14k views

What is the formula for finding the average atomic mass of an element based on the abundance of its isotopes?

In my class my teacher showed us how to find the average atomic mass of an element with a method, but he didn't really state a formula one could use. I came up with a formula of my own, and from what ...
8
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1answer
683 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: ...
8
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1answer
112 views

Continuous flow mass spectrometer for isotope analysis

If i took thousands of discrete samples of mineral fragments in a field study using a specialized drill, what mass-spectrometry techniques/equipment would allow me to analyse the samples as fast as ...
7
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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 ...
7
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2answers
5k views

Why is there no neutron in protium?

My chemistry teacher once told me, that every atom should have at least as many neutrons as protons, to keep the electrons from crashing into the nucleus. Protium, however, doesn't even have ...
7
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2answers
747 views

How can we accurately carbon-date samples from La Brea?

TL;DR - given a sample of bone which has been encased in asphalt for tens of thousands of years and has become saturated with the asphalt, how can you get an accurate age for the specimen through ...
7
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1answer
623 views

Why is Nitrogen 15 found almost exclusively in marine environments?

Prelude The following story was told to me earlier this summer Every year during October, the Pacific rain creates an ideal spawning condition for the wild Pacific salmon in the coastal forests of ...
7
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1answer
599 views

E1 and E2 elimination reactions of isotopically labeled bromocyclohexanes

Question a) What would the product of the reaction be for an E2 mechanism b) What would the products be for an E1 mechanism The Br coming out of the page is the 79 isotope while the ...
7
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1answer
515 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 ...
7
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1answer
4k 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 ...
7
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1answer
2k views

Specific Heat Capacity of Heavy Water

Water has an unusually high specific heat capacity due to it's hydrogen bonds. Why is it that the change in isotope causes a 10% difference in the heat capacity? How does the added neutron in the ...
6
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2answers
6k views

The effects of adding neutrons to an atom

So neutrons are neutral in terms of charge, and adding neutrons to an atom affects its atomic mass. But when neutrons are added to the nucleus, the nuclear radius would be affected. Couldn't that ...
6
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1answer
128 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 ...
5
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2answers
499 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 ...
5
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2answers
63 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 ...
5
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3answers
238 views

Can I perform a stable isotope analysis at home?

I'm interested in measuring the stable isotope ratios of some bird feathers. I'm aware that a mass spectrometer is required to measure stable isotope ratios. Is it possible to measure stable isotope ...
5
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1answer
605 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 ...