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Isotopes and mass spectrometers

Page history last edited by PBworks 16 years, 4 months ago

by Hannah, Ryan, Cal

The Isotope was discovered at the end of the 19th century the scientist Federick Soddy from England and Kasimir Fajans both discovered through observation these radioactive substances and named them Isotopes.


An Isotope is an atom whith a differnt number of neutrons than protons.


In 1919, two years after the end of the first world war Francis Aston created the mass spectograph to find isotopes of Neon. The mass spectrograph was later used by scientist Gyorgy Hevesy's in the study of radioactive lead isotopes to study plant growth.


The mass spectrometer is an instrument which can measure the masses and relative concentrations of atoms and molecules. It makes use of the basic magnetic force on a moving object.



The picture above shows how a mass spectrometer works. Particles moving into the spectrometer are charged and pass into a tube which conducts the particles down where they are introduced into a magnetic field which provides the centripetal force to bend the charge into a circle of a radius. All the processes in a mass spectrometer take place in a vacuum.


An easy way to understand Mass Spectrometers is to visualize a canonball coming at you and you wanted to change the course of the cannonball by squirting a water hose at it. Because the mass of the cannonball is so large, it would hardly be moved. However, if instead of a cannonball a ping pong ball was shot toward you the hose would greatly affect the path of the ball, because the mass of the ball would be less than the force being exerted on it. In a mass spectrometer the magnetic field acts in the same way as the hose, causing the particles to veer off course. By calculating the speed of the object and the change in course, it is possible to calculate the mass of the object.

A Mass Spectrometer


The mass spectrometer is used to characterize isotopes. It does so by organizing isotopes with there mass, their abundance in nature and how many different isotopes of a certain element actually exist.


Why would anyone need to know the mass of an atom?


Archeologists use mass spectrometers in order to find the mass of a specific isotope, Carbon 14. Carbon 14 which is radioactive and slowly decays with time gives archeologists a very good idea of the age of artifacts. This is known as Carbon dating.


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"Isotopes." Encyclopedia of Earth and Physical Science. New York: Marshall Cavendish, 1998. 628 – 631.


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Mass Spectrometer. 4 Oct. 2006 <http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic.html>.


Nier, Alfred O, and Harry E Gove. Mass Spectroscope. 2002. 4 Oct. 2006<http://www.accesscience.com>.


Nobel Prizes in Science. 20 June 2005. 4 Oct. 2006 <http://www.lbl.gov/abc/ wallchart/chapters/appendix.html>.


Volti, Rudi. "Isotopes." The Facts on File Encyclopedia of Science, Technology, and Society. Vol. 2. New York: Facts on File, 1999. 84, 561, 748.

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