atomic percent
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The atomic ratio is a measure of the
ratio In mathematics, a ratio shows how many times one number contains another. For example, if there are eight oranges and six lemons in a bowl of fruit, then the ratio of oranges to lemons is eight to six (that is, 8:6, which is equivalent to the ...
of atoms of one kind (i) to another kind (j). A closely related concept is the atomic percent (or at.%), which gives the percentage of one kind of atom relative to the total number of atoms. The molecular equivalents of these concepts are the molar fraction, or molar percent.


Atoms

Mathematically, the ''atomic percent'' is : \mathrm \ (\mathrm) = \frac \times 100 \ % where ''N''i are the number of atoms of interest and ''N''tot are the total number of atoms, while the ''atomic ratio'' is : \mathrm \ (\mathrm) = \mathrm \ (\mathrm) : \mathrm \ (\mathrm) \ . For example, the ''atomic percent'' of
hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic ...
in
water Water (chemical formula ) is an Inorganic compound, inorganic, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living ...
(H2O) is , while the ''atomic ratio'' of hydrogen to oxygen is .


Isotopes

Another application is in
radiochemistry Radiochemistry is the chemistry of radioactive materials, where radioactive isotopes of elements are used to study the properties and chemical reactions of non-radioactive isotopes (often within radiochemistry the absence of radioactivity leads t ...
, where this may refer to isotopic ratios or
isotopic abundance 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 atomi ...
s. Mathematically, the ''isotopic abundance'' is : \mathrm \ (\mathrm) = \frac \ , where ''N''i are the number of atoms of the isotope of interest and ''N''tot is the total number of atoms, while the ''atomic ratio'' is : \mathrm \ (\mathrm) = \mathrm \ (\mathrm) : \mathrm \ (\mathrm) \ . For example, the ''isotopic ratio'' of
deuterium Deuterium (or hydrogen-2, symbol or deuterium, also known as heavy hydrogen) is one of two stable isotopes of hydrogen (the other being protium, or hydrogen-1). The nucleus of a deuterium atom, called a deuteron, contains one proton and one ...
(D) to
hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic ...
(H) in heavy water is roughly (corresponding to an ''isotopic abundance'' of 0.00014%).


Doping in laser physics

In
laser physics Laser science or laser physics is a branch of optics that describes the theory and practice of lasers. Laser science is principally concerned with quantum electronics, laser construction, optical cavity design, the physics of producing a popula ...
however, the ''atomic ratio'' may refer to the doping ratio or the doping fraction. *For example, theoretically, a 100% ''doping ratio'' of Yb : Y3Al5O12 is pure Yb3Al5O12. *The ''doping fraction'' equals, ::::::::\mathrm \frac


See also

* Table of concentration measures


References

Physical chemistry {{physical-chemistry-stub