Home
>
The Basics
Atoms
+ Isotopes +
Units
+
Fission
+
Radiation
+
Neutrons
+
Applications
<h2>Isotopes</h2> <p>So far we have seen that different numbers of protons in an atom's nucleus gives us different elements. The number of protons is what makes nitrogen behave like nitrogen and not any other element.</p> <p>Changing the number of electrons in an atom affects the overall electrical charge of that atom, but it remains an ion of the same element. So what effect does it have on an atom if we change the number of neutrons?</p> <p>We get a different version of the same atom that has a different weight: an isotope.</p> <p>The prefix "iso" means "the same", indicating that the two atoms are the same element, just that one is heavier than the other. For example helium has two protons in its nucleus. The common form of helium has two neutrons in the nucleus as well, but there is a lighter isotope of helium with only one neutron. We refer to isotopes by their name and weight, so instead of just taking about helium or carbon, we talk about helium-3 and helium-4 or carbon-14 and carbon-12. The atomic weight is the total number of protons and neutrons in the nucleus (because we know electrons are so much smaller they contribute little to the atom's weight). So helium-3 is the lighter form of helium with a nucleus containing two protons and one neutron. In short notation 3 helium-3 is written He.</p> <p>Unlike changes in the number of electrons, changing the neutrons in an atom does not affect the chemical properties of that atom. It remains the same element and behaves the same way toward other elements. In chemical terms, two isotopes of zinc will behave in the same way as each other.</p> <p>Isotopes however have different <em>nuclear</em> properties.</p> <p> <a href="basics3.html" target="_top">next ></a></p>
