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Natural Abundance

Quick Reference
Also Known AsIsotope natural abundance, relative isotope abundance, atom percent

What is Natural Abundance?

The percentage of a particular isotope found naturally on Earth relative to the total amount of that element. For example, carbon-12 has a natural abundance of about 98.9% and carbon-13 about 1.1%. Natural abundances determine the atomic weight of elements.

Properties & Characteristics

Natural abundance refers to the percentage of each isotope of an element as found in naturally occurring samples. It is expressed as atom percent (or mole fraction). For example: ¹²C = 98.93%, ¹³C = 1.07%; ¹H = 99.985%, ²H = 0.015%; ²³⁸U = 99.27%, ²³⁵U = 0.72%. Natural abundances are nearly constant on Earth but vary slightly between geological sources. They are used to calculate average atomic masses in the periodic table.

Uses & Applications

Natural abundance values are used in: calculating average atomic masses (standard atomic weights), designing NMR experiments (¹H NMR exploits 99.985% natural abundance; ¹³C NMR sensitivity is low at 1.07%), isotope ratio mass spectrometry (IRMS), nuclear fuel enrichment calculations (increasing ²³⁵U above its 0.72% natural level), and in isotope geology.

Safety Information

No direct safety concern for the concept. Knowledge of natural abundance guides assessment of radiation exposure from natural radioactive isotopes: ⁴⁰K (natural abundance 0.0117%) is present in all foods and the human body, contributing to natural background radiation.

Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.

Key Facts

Term Natural Abundance
Synonyms Isotope natural abundance, relative isotope abundance, atom percent

Frequently Asked Questions

The percentage of a particular isotope found naturally on Earth relative to the total amount of that element. For example, carbon-12 has a natural abundance of about 98.9% and carbon-13 about 1.1%. Natural abundances determine the atomic weight of elements.

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