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).
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...
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 =...
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...
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.
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...
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...
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) +...
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...
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...
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...
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
...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"...
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...
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.
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...
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...
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).
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?
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?
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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
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:
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...
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?
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!
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...
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 =...
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...
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?
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
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...
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...
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...
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...
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."...
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!