In chemistry, 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) 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.
As an example, uranium has three naturally occurring isotopes: 238U, 235U and 234U. Their respective NA range from 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 99,275 238U atoms, 720 235U atoms, and no more than 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 to 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 billion years ago the NA of 235U was 3.1% compared to 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 by natural radioactive isotopes (as in the case of radiogenic isotopes of lead).
Deviations from natural abundance
It is now known from study of the sun and primitive meteorites that the solar system was initially almost homogeneous in isotopic composition. Deviations from the (evolving) galactic average, locally-sampled around the time that the sun's nuclear burning began, can generally be accounted for by mass fractionation (see the article on mass-independent fractionation) plus a limited number of nuclear decay and transmutation processes. There is also evidence for injection of short-lived (now extinct) isotopes from a nearby supernova explosion that may have triggered solar nebula collapse. Hence deviations from natural abundance on earth are often measured in parts per thousand (per mil or ‰) because they are less than one percent (%). The single exception to this lies with the presolar grains found in primitive meteorites. These bypassed the homogenization, and often carry the nuclear signature of specific nucleosynthesis processes in which their elements were made. In these materials, deviations from "natural abundance" are sometimes measured in factors of 100.
Footnotes and References
- ^ Uranium Isotopes, retrieved 14 March 2012
- ^ Robert N. Clayton (1978) Isotopic anomalies in the early solar system, Annual Review of Nuclear and Particle Science 28:501-522.
- ^ Ernst Zinner (2003) An isotopic view of the early solar system, Science 300:5617, 265-267.
- ^ Ernst Zinner (1998) Stellar nucleosynthesis and the isotopic composition of presolar grains from primitive meteorites, Annual Review of Earth and Planetary Sciences 26:147-188.
Atomic Mass: How to Calculate Isotope Abundance
To see all my Chemistry videos, check out http://socratic.org/chemistry How do you determine and calculate isotope abundance when you know the relative atomi...
How to Find the Abundance of Each Isotope
If you're given the mass of each isotope of an element, and the average atomic mass, you can calculate the percent (%) abundance of each isotope. Let "x" be ...
Calculating Isotope Abundance using Atomic Mass
webpage-http://www.kentchemistry.com/links/AtomicStructure/atomicmasscalc.htm This is a more challenging problem using atomic mass. I show you haw to calcula...
Calculating Isotopic Abundance Example
The following video is on isotopes and calculating average atomic mass of various atoms. For more science and math podcasts search Papapodcasts in iTunes.
Calculating Atomic Mass from Natural Abundances
This video is an example of how to find the atomic mass of an element by using the mass of each isotope and their respective abundances. Check out my website...
Natural Abundance, The Lessons Learned, Applying Them
Natural Abundance, The Lessons Learned, Applying Them To Improve Human Settlements/Communities here is some health/nutrition info on mulberry's http://lifest...
True Story: Tap Your Natural Abundance - Monkey Metaphor
http://mindpersuasion.com Once upon a time there was a young monkey. He had been separated from his family when he was very young, and while he didn't rememb...
Seth on Embracing your Natural Abundance by Jane Roberts
Seth discusses the importance of embracing your own natural abundance. This audio clip is from the Seth Audio Collection, Volume 1, Disc 1. For more informat...
Natural abundance, the universe is abundant in nature
Life IS abundance. Life IS a miracle. Life IS infinite~ Yes we are living in a world of contrast. Yes we experience separation, duality, preference, pain, pl...
Ahhh... Natural Abundance! Sept 27, 2013 - CindyEyler Vlog
40 Day Manifesting Breakthrough Video eCourse: http://www.cindyeyler.com/manifesting-breakthroughs/ http://www.CindyEyler.com http://SoulTravelEgypt.WordPres...
Comox Vallety Record
Wed, 16 Apr 2014 14:56:15 -0700
The abundance of product from wine to oysters and everything in between in the Comox Valley is evident to locals, but is also growing in popularity for those elsewhere. The growth, particularly targeting those outside the Valley, is creating a growing ...
Mon, 21 Apr 2014 09:52:30 -0700
A natural abundance of seeds, berries, and caterpillars will do more for backyard birds than any buffet you can provide them—and will keep the unexpected dangers of artificial materials at bay. Share photos of your humane backyard on Facebook, Twitter ...
Tue, 15 Apr 2014 01:26:15 -0700
... including automotive catalytic converters and industrial catalysts (e.g. from the chemical and petrochemical industries) contain Precious Metals and specifically the Platinum Group Metals (PGMs) that are valuable as a result of their low natural ...
Huffington Post Canada
Tue, 15 Apr 2014 09:54:05 -0700
Around the world, we have built most of our cities in places of high biodiversity and places of natural abundance, such as coastal areas, river valleys and habitat edges. In cities like Toronto, while we have almost obliterated the original landscape ...
Mon, 14 Apr 2014 03:30:00 -0700
Precious Metals and specifically the Platinum Group Metals (PGM's) are valuable because of their low natural abundance, their unique properties and the complex processes that are required for their extraction and refining from primary sources. While ...
Twain Harte News
Twain Harte News
Fri, 11 Apr 2014 13:58:29 -0700
... connection with people you might normally tend to pass by and take for granted. 3. Use a skill or talent you have – cooking, accounting, decorating – to help someone who could benefit from it. It will reconnect you to the natural abundance in your ...
Thu, 17 Apr 2014 04:48:45 -0700
With its high theoretical capacity, natural abundance, low cost and environmental benignity, Fe3O4 is an appealing alternative anode material for lithium-ion batteries. However, similar to other transition metal oxides (MxOy), it has an extremely low ...
Sat, 29 Mar 2014 22:00:24 -0700
A place of natural abundance in the heart of the crowded suburbs, the bioreserve has long served as a haven for hikers, dog walkers, bird watchers, hunters, cross-country skiers, and other outdoors lovers. Provencher, a land protection specialist for ...
Oops, we seem to be having trouble contacting Twitter
You can talk about Natural abundance with people all over the world in our discussions.