What is Abundance: Definition and 47 Discussions

In physics, natural abundance (NA) refers to the abundance of isotopes of a chemical element as naturally found on a planet. The relative atomic mass (a weighted average, weighted by mole-fraction abundance figures) of these isotopes is the atomic weight listed for the element in the periodic table. The abundance of an isotope varies from planet to planet, and even from place to place on the Earth, but remains relatively constant in time (on a short-term scale).
As an example, uranium has three naturally occurring isotopes: 238U, 235U and 234U. Their respective natural mole-fraction abundances are 99.2739–99.2752%, 0.7198–0.7202%, and 0.0050–0.0059%. For example, if 100,000 uranium atoms were analyzed, one would expect to find approximately 99,274 238U atoms, approximately 720 235U atoms, and very few (most likely 5 or 6) 234U atoms. This is because 238U is much more stable than 235U or 234U, as the half-life of each isotope reveals: 4.468 × 109 years for 238U compared with 7.038 × 108 years for 235U and 245,500 years for 234U.
Exactly because the different uranium isotopes have different half-lives, when the Earth was younger, the isotopic composition of uranium was different. As an example, 1.7×109 years ago the NA of 235U was 3.1% compared with today's 0.7%, and for that reason a natural nuclear fission reactor was able to form, something that cannot happen today.
However, the natural abundance of a given isotope is also affected by the probability of its creation in nucleosynthesis (as in the case of samarium; radioactive 147Sm and 148Sm are much more abundant than stable 144Sm) and by production of a given isotope as a daughter of natural radioactive isotopes (as in the case of radiogenic isotopes of lead).

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  1. gurbir_s

    A Solving this first-order differential equation for neutron abundance

    The time rate of change of neutron abundance ##X_n## is given by $$\frac{dX_n}{dt} = \lambda - (\lambda + \hat\lambda)X_n$$ where ##\lambda## is neutron production rate per proton and ##\hat\lambda## is neutron destruction rate per neutron. Given the values of ##\lambda## and ##\hat\lambda## at...
  2. S

    Explosive Nucleosynthesis Yields - Abundance Calculations

    If we consider for Oxygen: - Using the solar values from Anders and Grevesse, where O_⊙ = 8.51e-04 and Si_⊙ = 3.55e-05 (abundances number relative to H). - Using the explosion model 40A from Maeda+2003 (Table 2), we know the ejecta mass (in solar units) for: oxygen-16 = 5.99 oxygen-17 =...
  3. koulbichok

    I Gaussian probability distribution of formation PBH

    Hello. If we consider PBH formation from collapse of large density perturbation in the early Universe, a mass PBH depends on density contrast as And δ must be larger then . Also we have β — an abundance of black holes, it's the ratio of the PBH energy density to the total energy density, this...
  4. koulbichok

    A Abundance and mass spectrum of PBH

    Hello. I'm trying to study primordial black holes for my work, but I still can't understand what are abundance and mass spectrum? Could you explain? Thanks in advance.
  5. P

    How would you solve the water abundance XPrize?

    Hi everyone, This was the criteria for the competition: The Water Abundance Prize tasks competing teams with developing technologies that can harvest 2,000 liters (528 gal) of water from the atmosphere each day, using only renewable energy at a cost of no more than two centers per liter (0.26...
  6. Guilherme Franco

    A Are period 5 elements common in most stars?

    My question might seem simple, however I couldn't find data on this. Let me explain my situation: I'm involved in a project about the formulation of new criteria to avaliate exoplanetary systems for search of extraterrestrial intelligence. The key question is mostly around the element...
  7. 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) +...
  8. T

    I Ratio of abundance of sub-atomic particles in the universe?

    I was wondering if there is a current hypothesis about the quantities of which matter particles were created? I'm not completely au fait with the standard model, but I've seen the picture...
  9. Buzz Bloom

    Question re equilibrium abundance of a protons and electrons

    I am thinking of a time period between two events: 1. After the annihilation of most protons/neutrons with all anti-protons/anti-neutrons, and 2. Before the annihilation of electrons and positrons. During this period the temperature decreases from T1 to T2. T1 is the highest temperature at...
  10. Buzz Bloom

    I Question about relative abundance of particles before annihilation

    I am looking to correct my understanding about the relative abundance of particles and antiparticles created before the two periods of annihilation: (1) protons/neutrons and anti-protons/anti-neutrons, and (2) electrons and positrons. In a previous thread...
  11. vmr101

    Solve these equations numerically - Stellar Abundance Ratios

    1. Question from a textbook. I have written down the differential equations for part a) and shown part b), but I am unsure of how to tackle part c). 2. This is the Question from the book http://www.m-rossi.com/img/asp3012-1.png Any advice would be grateful. Thank you
  12. V

    How abundant is each elementary particle in nature?

    ...and what form may they found normally? Somebody asked me just how many of the particles we know are possible (say, delta baryons) can be found in nature and what is their usual state - are there many particles to be found outside of atoms? Although there are enough "abundance of elements"...
  13. Astronuc

    News Shortage in the midst of abundance

    Earlier this year, I experienced a spike in the cost of electricity such that we nearly spent twice as much during Jan-Feb than during the same period a year earlier, and we used less electricity than last year. The argument from the local utility was that there was a shortage, despite abundant...
  14. M

    A question on the abundance of the elements

    How can scientists determine,calculate or understand that in the universe hydrogen is the most abundunt element as there are thousands of galaxy with their own planets. There might even an undiscovered element that could be most abundunt. Have a nice day.
  15. P

    Astronomy: abundance, concentration, density

    Homework Statement Hi. I feel like this is probably very basic. Basically, I'm trying to understand how surface density * concentration = abundance I'm reading about gas surface density in the galaxy and its relationship to star formation, gas ejection etc. And we are given an...
  16. E

    Calculating natural abundance.

    I thought this area was appropriate for this question from a previous exam paper which I just need checking. So: Working out: The half-life of 244Hb is 10 million years. The half-life of 244Hb is 5.2595×10^12 minutes. The mean life of 244Hb is 7.58783677×10^12 minutes. So if you...
  17. M

    What determines the abundance of elements?

    I was just watching a very particular old documentary, when the question hit me. I could probably manage an educated guess, but I don't really know what exactly determines how much of a certain element there is(except H and He, those are obvious).
  18. D

    Elemental Abundance in Stars - The Curve of Growth

    I am studying for my undergraduate Astrophysics module and the lectures notes say that that all abundances are measured relative, in terms of H = 12.00 by mass or number of atoms. Is this correct? I thought it was all based off of Carbon = 12. Am I missing something?
  19. mishima

    Relative Abundance of Light Frequencies?

    I was curious if anyone had ever seen information about how often one frequency of electromagnetic radiation appears in the universe compared to the other. What is the most common frequency or range of frequencies, etc? Is there a way to even estimate this?
  20. S

    Calculating % Abundance of Br-79 & Br-81

    Homework Statement Naturally occurring bromine contains two isotopes; Br-79, which has a weight of 78.9183 and Br-81 with a weight of 80.9163. If the atomic weight of Br is 79.904, determine the % abundance of Br-79 and Br-81. Homework Equations To solve this equation I...
  21. TrickyDicky

    Light elements abundance in a static toy universe

    As an exercise in cosmology-fiction (I actually got curious about this from an actual cosmology textbook problem), taking into account the stellar nuclear reactions that involve the fusion of hydrogen into helium, what would (roughly) be the proportion (in mass) between Hydrogen and He-4 in a...
  22. B

    How to calculate species abundance and diversity

    Homework Statement This is the sample population taken along a 5m transect: ants:9 grasshoppers:1 pill bugs:4 spiders:1 Homework Equations What formulas would i use to calculate the species abundance and diversity? The Attempt at a Solution I only know this formula H'=-\Sigma...
  23. S

    Calculating percent abundance for 3 isotopes

    For my chemistry class, I need to be able to calculate percent abundances for multiples isotopes, if given the mass of the isotopes and average atomic mass of the element. The percent abundance of 1 isotope may be given. The teacher has said that calculating for a problem with 3 isotopes is...
  24. FeDeX_LaTeX

    Possible title: Isotope Abundance Calculations: Where Did I Go Wrong?

    Homework Statement 1) "The relative atomic mass of antimony is 121.8. Antimony exists as two isotopes; antimony-121 and antimony-123. Calculate the relative abundances of the two isotopes." 2) "The relative atomic mass of rubidium is 85.5. Rubidium consists of two isotopes, rubidium-85 and...
  25. S

    What is the ratio of hydrogen to helium in the Sun?

    Hi everyone, There is problem that asks how many hydrogen atoms are there in sun for each helium atom. I don't know which solution is correct: 1) to count all the hydrogens and heliums participating in one solar pp chain, or, 2) as X=0.71 and Y=0.26, there is (0.71/0.26)*2 H for each He...
  26. V

    Helium Abundance in ISM of Galaxies: Best-Estimate Value

    Hi, Here is an info I don't manage to obtain from anywhere so far ! What is the "best-estimate" of the Helium abundance (the He/H ratio) in the interstellar medium of galaxies in the nearby Universe and at high redshift? I know the primordial He abundance is Y = 0.24 but what is the...
  27. M

    Isotopic Abundance: What is it and how does it affect nuclear processes?

    Hello I'm new to Nuclear Physics and I'm stuck in understanding the Isotopic Abundance the book I am reading says this : "The isotopic abundance of the i-th isotope in a given element is the fraction of the atoms in the element that are that isotope." can you explain this please?or just...
  28. S

    Abundance of isotopes based on ratios

    Homework Statement how do i find abundances of isotopes of strontium if i am give their isotopic ratios and atomic masses Homework Equations The Attempt at a Solution i know i have to find what the mass of each isotope is in the ratios to find the % abundance. i don't want to put up...
  29. TrickyDicky

    New red dwarf count and He-4 abundance

    Does the new estimate on the number of red dwarf stars in the universe suggest a different proportion of He/H? (current helium abundance estimate is 24%) Would it be lower since more mass would be tied up in low-mass stars (like red dwarfs) in which He/H<0.24.? If not, how many more times should...
  30. TrickyDicky

    Exploring Stellar Nucleosynthesis and the Mystery of Helium-4 Abundance

    Hi, I would like to know the standard explanation about stellar nucleosynthesis of Helium-4 not being able to account for the observed He-4 abundance. Thanks
  31. A

    What Are the Benefits of Eating Traktkantarell Mushrooms?

    An abundance of yellow legs! The mushroom season is upon me, and this week-end, I picked 7.5 kg of this fellow: http://www.mediabasen.no/d/22616-2/Traktkantarell+045.jpg They're yummy good! :smile:
  32. N

    Decay - Abundance of Multiple Isotopes

    Homework Statement An element Z has two isotopes Z1 and Z2 with decay constants of λ1 and λ2. The natural activity of natural occurring element Z is A. What is the abundance of each isotope? Assume that these decay constants are long - the abundance of the element over time does not...
  33. K

    What is the percent abundance of 140Ce in Cerium?

    i am trying to figure out the percent abundance of two isotopes. i know how to set up the problem but i don't know how to find the weight of each isotopes. here is the problem: Cerium (58Ce) has two commonly occurring isotopes, 140Ce and 142Ce. what is the approximate percent abundance of 140Ce?
  34. G

    Element abundance on earth's crust

    May anyone help me on how to define the units used to define the abundance of elements on Earth's crust "It's written ppb(parts per billion by weight)" I really fail to define that!
  35. T

    CHEM - Uranium isotope relative abundance at diff times

    1. Homework Statement The relative abundance of uranium isotopes in today’s Earth crustal material is: 99.2745% 238U 0.7196% 235U 0.0055% 234U What were the relative abundances when the Earth was formed 4.6x109 years ago? 2. Homework Equations t = age = 1/lambda * ln(N/No) N...
  36. T

    Uranium isotope relative abundance at diff times

    Homework Statement The relative abundance of uranium isotopes in today’s Earth crustal material is: 99.2745% 238U 0.7196% 235U 0.0055% 234U What were the relative abundances when the Earth was formed 4.6x109 years ago? Homework Equations t = age = 1/lambda * ln(N/No) N =...
  37. S

    How to find abundance of 206, 207 and 208 Pb

    how would i find the abundance of Pb 206, 207 and 208 if I am given the isotopic data of 207Pb/206Pb and 208Pb/206Pb?
  38. C

    Finding mass based on amu and % abundance

    Homework Statement Oxygen has 3 isotopes. Oxygen-16 has the amu of 15.995 and its natural percent abundance is 99.759. Oxygen-17 has a mass of 16.995 amu and its natural percent abundance is 0.037. Oxygen-18 has a mass of 17.999 amu and its natural percent abundance is 0.204. What is the...
  39. A

    Why is there greater abundance of light than heavy elements on earth?

    Why there is on Earth stronger abundance of light elements. I mean elements that have proton number lower than 30. And are there any elements in nature in elemental(atomic) form?
  40. P

    What are the Weighted Averages of Element X Isotopes: 31x and 34x?

    Element x has two naturally occurring isotopes. The masses (amu) and % abundance are given. 31x is 35% with mass of 31.16 and 34x is 64% with 34.3 amu's
  41. Norman

    Abundance of small (about 1/8 inch) brownish reddish ants

    Hi All, I thought I would tap the collective brain to help solve an ant problem that we have in our new apartment. We have an abundance of small (about 1/8 inch) brownish reddish ants. They are definitely in the walls and on both floors of our house. I have been baiting for about 3 weeks...
  42. A

    Abundance of deuterium vs tritium

    In a nuclear fusion reactor for generating electricity, would a deuterium-deuterium reaction be inferior to a deuterium-tritium reaction? If the latter is a superior mode of fusion, then obviously that would be more preferable. But how abundant is tritium as an isotope, compared to deuterium, in...
  43. M

    Percent Abundance of Br-81 in Bromine

    Br consists of Br-79 and Br-81. The atomic mass of Br is 79.9. Find the % of Br-81 in bromine.
  44. wolram

    Under abundance of lithium may solve existence DM

    http://arxiv.org/PS_cache/hep-ph/pdf/0306/0306024.pdf Cold dark matter may be made of superweakly-interacting massive particles, superWIMPs, that naturally inherit the desired relic density from late decays of metastable WIMPs. Well-motivated examples are weak-scale gravitinos in...
  45. C

    Do many asteroids contain materials useful to civilization in abundance?

    I don't know if this is the correct section or not, but I'll let hosts and mentors decide that. My question comes as a result of hearing a number of things floating around as to the possibility of mining asteroids for materiasl valuable to space colonies. Do many asteroids contain...
  46. brum

    The problem with abundance (link)

    the problem with abundance... (link) "What do traffic jams, obesity and spam have in common? They are all problems caused by abundance in a world more attuned to scarcity. By achieving the goal of abundance, technology renders the natural checks and balances of scarcity obsolete."...
  47. S

    Understanding Relative Abundance in Chemistry: A Comprehensive Guide

    Man, I have a lab report for Chemistry due on Monday, and I've been working on in for a week. I have one problem. What does relative abundance tell you? I've searched on Google and even looked in the index of my Chemistry book. Nada. Nil. Cero. Any help is very much appreciated!