[ ChemNews 9 ]

Isotopes

        Isotopes are atoms with the same number of protons, but differing numbers of neutrons. In other words, the have different atomic weights. Isotopes are different forms of a single element.
        There are 275 isotopes of the 81 stable elements. There are over 800 radioactive isotopes, some of which are natural and some synthetic. Every element on the periodic table has multiple isotope forms.
        The chemical properties of isotopes of a single element tend to be nearly identical. The exception would be the isotopes of hydrogen since the number of neutrons has such a significant effect on the size of the hydrogen nucleus. The physical properties of  isotopes are different from each other since these properties often depend on mass.                This difference may be used to separate isotopes of an element from each other by using fractional distillation and diffusion.


       With the exception of hydrogen, the most abundant isotopes of the natural elements have the same number of protons and neutrons. The most abundant form of hydrogen is protium, which has one proton and no neutrons.

Isotope Notation
There are a couple of common ways to indicate isotopes:

• List the mass number of an element after its name or element symbol. For example, an isotope with 6 protons and 6 neutrons is carbon-12 or C-12. An isotope with 6 protons and 7 neutrons is carbon-13 or C-16. Note the mass number of two isotopes may be the same, even though they are different elements. For example, you could have carbon-14 and nitrogen-14.
• The mass number may be given in the upper left side of an element symbol. (Technically the mass number and atomic number should be stacked in line with each other, but they don't always line up on a computer.) For example, the isotopes of hydrogen may be written: 11H, 21H, 31H

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