What is Isotopes: Definition and 93 Discussions

Isotopes are two or more types of atoms that have the same atomic number (number of protons in their nuclei) and position in the periodic table (and hence belong to the same chemical element), and that differ in nucleon numbers (mass numbers) due to different numbers of neutrons in their nuclei. While all isotopes of a given element have almost the same chemical properties, they have different atomic masses and physical properties.The term isotope is formed from the Greek roots isos (ἴσος "equal") and topos (τόπος "place"), meaning "the same place"; thus, the meaning behind the name is that different isotopes of a single element occupy the same position on the periodic table. It was coined by Scottish doctor and writer Margaret Todd in 1913 in a suggestion to chemist Frederick Soddy.
The number of protons within the atom's nucleus is called atomic number and is equal to the number of electrons in the neutral (non-ionized) atom. Each atomic number identifies a specific element, but not the isotope; an atom of a given element may have a wide range in its number of neutrons. The number of nucleons (both protons and neutrons) in the nucleus is the atom's mass number, and each isotope of a given element has a different mass number.
For example, carbon-12, carbon-13, and carbon-14 are three isotopes of the element carbon with mass numbers 12, 13, and 14, respectively. The atomic number of carbon is 6, which means that every carbon atom has 6 protons so that the neutron numbers of these isotopes are 6, 7, and 8 respectively.

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  1. Astronuc

    B FRIB creates five new isotopes (Tm-182,-183; Yb-186,-187; Lu-190)

    https://frib.msu.edu/news/2024/new-isotopes Physcial Review Letters https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.132.072501 198Pt atoms of 186 MeV/u were directed onto a carbon target; primary beam power was 1.5 kW. https://frib.msu.edu/
  2. F

    I Having problems finding an equation for radioisotope production yield

    I am trying to get a plot, or a result for target like this: I've found some equations for my requested results, but they are from the same person's articles and I couldn't find another source. I've searched for EOB and TTY calculations but couldn't really do something. Could you give me an...
  3. M

    Hypothetical stable isotope of Promethium?

    Say one was to create an artificial stable isotope of Promethium as it has predicted applicable properties. What would it’s number have to be? I know Promethium-147 is semi-stable.
  4. mesa

    Looking for a digital copy of the Table of Radioactive Isotopes

    Hello all, I am looking to get an electronic copy of the Table of Radioactive Isotopes by Edgardo Browne and Richard B. Firestone. I know that we can run software that incorporates this database here: https://www2.lbl.gov/LBL-Programs/Gamquest.html , but I am looking for an electronic copy to...
  5. J

    Understanding radioactivity levels of different isotopes

    Homework Statement:: Understanding radioactivity levels of different isotopes Relevant Equations:: None Hi, This isn't a homework problem but is an introductory question. Could someone explains what makes one isotope more radioactive than another isotope assuming you have the same amount of...
  6. PainterGuy

    Why wasn't fluorine used as a standard for atomic mass?

    Hi, I found the two sections in red a little confusing. I'd appreciate it if you could help me with it. Source: https://en.wikipedia.org/wiki/Atomic_mass#History The existence of isotopes was first suggested around 1913[reference]. The first periodic table by Mendeleev in 1869 used...
  7. Admiralibr123

    I Looking for Experimental Data on Isotopes (Nuclear Physics and Engineering)

    So, a website in which I just enter an element or an Isotope and it just lists all the relevant experimental data like mass, mass-defect binding energy etc. Also resources for the absorption data, resources to explore Monte-Carlo simulations, and other calculation tools would be awesome. Just a...
  8. ORF

    Do carnivores have a higher proportion of light isotopes than plants?

    Hello, because of the "kinetic isotopic effect", https://en.m.wikipedia.org/wiki/Kinetic_isotope_effect can the ratio of the common isotopes of N, C, P, H, O, S determine the position of an individual in the food chain? (eg, have carnivore animals higher proportion of light isotopes than...
  9. Basil Currie

    B What is the Most Efficient Fuel for Fusion Reactors: T-D, D-D, or D+He-3?

    Hi, Does a T-D or a D-D fusion release more energy? Even if D-D needs higher temperatures, would it produce more energy in a fusion reactor?
  10. Navin

    Dipole moment carbon florides of isotopes of Hydrogen

    Homework Statement Compare Dipole moment of CH3F and and CD3F where D is deuterium. Homework Equations Theory questions The Attempt at a Solution Our sir had explained that to do this question we muat take into account the vibration of the atom in the respective molecule. That is that the...
  11. S

    B Is Radioactive Decay Truly Random?

    How can radioactive decay be random if we can calculate aproximately when it will happen . For example we know that an isotope will decay every 2 years by calculating the half life . Doesnt that mean that the decay is systematic rather than random because we can calculate when its guna happen ...
  12. J

    B Terrestrial Spontaneous Fission & Unstable Isotopes

    Does terrestrial spontaneous fission or natural fission create unstable isotopes similar to nuclear fission in reactors?
  13. prashantakerkar

    Isotope applications in Agriculture industry

    https://en.m.wikipedia.org/wiki/Isotope Can Isotopes be useful to Agriculture industry viz Fertilizers & Instecticides manufacturing? Thanks & Regards, Prashant S Akerkar
  14. S

    Percent composition of Silver (two naturally occurring isotopes)

    Homework Statement Silver has two naturally occurring isotopes: Ag−107 with a mass of 106.905 amu and a natural abundance of 51.84 %, and Ag−109. Use the atomic mass of silver listed in the periodic table to determine the mass of Ag−109. express answer to 4 sig-figs and use appropriate units...
  15. nomadreid

    I Uranium isotopes with m in superscript

    On the page https://en.wikipedia.org/wiki/Isotopes_of_uranium, some of the superscripts have, besides the atomic number, also an "m". For example, besides the usual isotope 234U with spin 0+, there is also the isotope 234mU (with nuclear spin 6-). What is this "m"? While I am at it, what is the...
  16. S

    I Is there no stable isotope of Tungsten?

    I was looking at this neat graph of all the isotopes and which ones are stable and how they decay: https://upload.wikimedia.org/wikipedia/commons/thumb/c/c4/Table_isotopes_en.svg/715px-Table_isotopes_en.svg.png The black squares represent stable isotopes, and columns that have no such black...
  17. ORF

    Detailed history about the discovery of "isotopes"?

    Hello I would like to know more about the history of the discovery of the isotopes, what there was before, and the short term impact on the chemistry and nuclear physics. Is this topic discussed in any book/review? Thank you for your time. Regards, ORF
  18. G

    I Understanding Isotopes: Exploring the Complexity of Radioactive Elements

    Hello,something I've always had some confusion with is the vast number of radioactive isotopes that form from fission and subsequent decay of the fissioned nuclei. first of all does anyone have a link or something to a good high resolution picture of a chemical elements periodic table kind of...
  19. S

    I Converting measured activity between isotopes

    Hello there, I have a question that I just can't seem to solve by myself (although compared to the other threads here it seems quite simple) I did some FDG-PET scans for my master thesis: I inject a certain dose of F18-FDG and prepare these injections by measuring the right dose using a...
  20. Strife_Cloud

    Uranium conversion / reprocessing TRU isotopes

    I am doing a study guide for a nuclear chemistry introductory course FINAL EXAM. A few of the questions have me confused because, although they are asked in a multiple-choice format, the prof. has indicated that multiple choices may be correct for given problems and that you must not only choose...
  21. Astronuc

    Radioisotopic dating with isotopes of different masses

    Read more at: https://phys.org/news/2017-01-paper-spotlights-key-flaw-widely.html#jCp Robert B. Hayes. Some Mathematical and Geophysical Considerations in Radioisotope Dating Applications, Nuclear Technology (2017). DOI: 10.13182/NT16-98 (Requires purchase or subscription)
  22. l0st

    I Is there a way to lower critical mass?

    Judging by https://en.wikipedia.org/wiki/Critical_mass , californium-252 has the lowest critical mass among known isotopes and isomeres. But it is still very high. Is there a way to reduce it significantly (down to microgramms) or, perhaps, a semi-stable isotope/isomere, which would have such a...
  23. Mrinmoy Naskar

    Why does uranium not have any stable isotopes?

    why uranium does not have any stable isotope?
  24. Clara Chung

    Why are activities of all isotopes in a decay-chain equal?

    For example the activity of U-238 and U-234 in an uranium series is the same. Isn't activity depends on decay constant and the amount of atoms? Why must the activities equal and what is the reason behind?
  25. moenste

    Speed, force, magnetic flux of an ion?

    Homework Statement The diagram shows a mass spectrometer used for measuring the masses of isotopes. It consists of an ion generator and accelerator, a velocity selector and an ion separator, all in a vacuum. In one experiment, tin ions, each of which carries a charge of +1.6 * 10-19 C, are...
  26. CMATT

    Isotopes, atomic mass, abundance

    Homework Statement Suppose the element A contains three isotopes, 86A (atomic mass 85.909 u, abundance 16.19%) 87A (atomic mass 86.908, abundance 7.00%) and 88A (atomic mass 87.906 u). What would be the atomic mass of A that would appear in the periodic table? Homework Equations (A1 x %A1) +...
  27. dovis

    Help with nuclear explosion released isotopes

    After a nuclear explosion in the environment remains a lot of half-life of a radioactive isotope . Which of them pose the greatest danger to people , find themselves in the same place after a certain time ? why?
  28. Elvis 123456789

    Distance between Isotopes in a mass spec

    Homework Statement Suppose the electric field between the plates P and P' in the mass spectrometer in following figure is 1.89×104V/m and the magnetic field in both regions is 0.668 T. If the source contains the three isotopes of krypton, 82Kr,84Kr, and 86Kr, and the ions are singly charged...
  29. A

    Uncovering the Mystery of Isotope Formation: The Role of Strong Interaction

    if protons don't have any for of charge and aren't attract to the nucleus then why are there isotopes?
  30. G

    Calculation of alpha particles from 226-Ra decay

    I am trying to solve the following problem for my graduate course in isotope geochemistry. If 1 g of 226Ra is separated from its decay products and then placed in a vessel, how much helium (cm3) will accumulate in the vessel in 60 days? Here is what I know. The decay series from 226Ra to Lead...
  31. Z

    Radioactive Isotopes and half life

    Homework Statement If a radioactive isotope ends with 55.5 g, and has a half-life of 2.5 days, how much was there 8.3 days ago? Homework Equations mf=mi(1/2^t/h) The Attempt at a Solution the answer i got was 554 g, is it correct?
  32. Mark lamorey

    What is the meaning of unbound in the context of half-lives of nuclei?

    I have been looking at half-life of various isotopes and many of the tables / information I am finding is giving energies (MeV, KeV) for certain half lifes. This does not make sense to me, am I missing something ? For example : http://ie.lbl.gov/toi/listnuc.asp?sql=&A1=5&A2=5 5Li and 5He give...
  33. Mark lamorey

    Looking for tabular data of Isotopes

    I am looking for tabular view of all isotopes (*.xls, *.csv, *.ods , ... ). Preferably with as much information as possible - half life, mean life, decay constant, specific activity, ... Any thoughts on where this might exist. I am wondering about correlations between stability and different...
  34. CAH

    Neutral isotopes of atom, state possible value for A & Z?

    A neutral atom of radium isotope may be represented by: 228 Ra (88 proton number, 228 nucleon number). 88...
  35. CivilSigma

    Is the decay constant , constant for all isotopes of element

    I have this true and false question: " The half life and therefore the decay constant will be the same for every isotope a) True b) False c) only if it is an isotope of the same element " I think this is false, just by intuition.
  36. 2

    How can metastable isotopes exist?

    I thought I would ask this question in the quantum mechanics section as I presume it has something to do with QM, like the reason why alpha and beta decay do not happen immediately but instead there is a half life for this decay. My understanding is that with alpha decay, the strong nuclear...
  37. S

    Calculating the Isotope Ratio of Uranium 235 and 238 4.5 Billion Years Ago

    Homework Statement Current share of Uranium isotope on Earth is 99.28% (##^{238}U##) and 0.72% (##^{235}U##), half-life times are ##7.04\cdot 10^8 years## (##^{235}U##) and ##4.468\cdot 10^9 years## (##^{238}U##). Calculate the ratio between the isotopes ##4.5\cdot 10^9 years## ago...
  38. C

    Isotopes: Proton vs Neutron Counts

    I'm in year 10 and I have been studying physics and chemistry. When I learned isotopes, I notice that for isotopes, the number of neutron is always higher than that of proton. Is it possible that there are isotopes that the number of neutron is lower than that of proton? If no, is that because...
  39. Toast

    Separative work, Enrichment of elements containing multiple isotopes

    Dear all I'm trying to find the separative work units (SWU) required to enrich isotopically Tungsten. I've come across the SWU equation (http://www.fas.org/programs/ssp/nukes/effects/swu.html) SWU = P·V(Np) + W·V(Nw) – F·V(Nf) where V(x)=(2x-1)ln(x/(1-x)) and x is the...
  40. H

    Uranium isotopes percentage 4.5 billion years ago

    Homework Statement Please help me solve this problem... Given T(1/2) of U-235 = 7.04x10^8 yrs (0.7%) T(1/2) 0f U-238 = 4.468x10^9 yrs (99.3%) Calculate percentage of U-235 & U-238 at the time of creation of earth(~4.5 billion years ago) Homework Equations N(t) = No e^(-λt) The...
  41. B

    Hydrogen isotopes in palladium

    I realize that Palladium has a molecular property to hold immense amounts of hydrogen, but can Palladium also “hold” isotopes of hydrogen.
  42. K

    Exploring Muonic Atoms: A Look at He Isotopes

    Casual searches for muonic atoms brings up various experiments on muonic hydrogen. The physics of this atom is fairly simple because the muon is just a heavier version of an electron. Has anyone studied atoms with both an electron and a muon around a nucleus, such a helium isotope? In this case...
  43. A

    Bromine Isotopes: Mass, Atomic Mass & Percent Abundance

    There are two different isotopes of bromine atoms. Under normal conditions, elemental bromine consists of molecules, and the mass of a molecule is the sum of the masses of the two atoms in the molecule. The mass spectrum of consists of three peaks: Mass Relative Size 157.836 0.2569 159.834...
  44. H

    Why do some unexpected isotopes occur naturally?

    Why do some isotopes occur naturally even though a seemingly valid decay with non-negligible energy release ~Mev, could energetically happen? E.g. Cadmium-106 could decay to Palladium-106 but it is still NATURALLY occurring?
  45. D

    Question related to rate of decay of unstable isotopes

    Homework Statement Two unstable isotopes A and B and a stable isotope C have the following decay rates per atom present: Let rate = k, A > B, k=k1=3 atoms/sec A > C, k=k2=1 atom/sec B > C, k=k3=2 atoms/sec Intially, there are N0 atoms of species A present, but none of other two types...
  46. H

    Why are neutron rich isotopes unstable

    Ive been researching for a while now and i still can't understand why neutrons rich isotopes are unstable. As neutrons act like the glue and hold protons together as they increase the Strong Nuclear force that act upon protons and neutrons, i thought the more neutrons the stronger they would...
  47. Z

    Calculating the mass of isotopes

    The spin values of each isotope of carbon are given on wiki here. When showing nuclear spin values the notation (1/2+)# is used. I don't understand what the () brackets and # hashtag are for? At the bottom of the page, they clarify it by saying: "Values marked # are not purely...
  48. D

    Half-life of radioactive isotopes near 0 K.

    Would the observed half-life of a sample of a radioactive isotope (eg. iodine 131) be different from the nominal half-life when it is cooled down to a temperature near absolute zero. Have there been any experiments conducted to examine this question?
  49. A

    Why aren't the daughter isotopes of alpha decay charged?

    For example, when a radioactive isotope of Uranium undergoes alpha decay, a radioactive isotope of Thorium is formed. Why isn't this daughter isotope charged?