Isotopes

If you look at the pictures you will see that there are two 'versions' of hydrogen. One of them has a nucleus containing a proton but the other has a nucleus with both a proton and a neutron. These two 'versions' of hydrogen are called ISOTOPES of hydrogen.


Almost all elements have naturally occurring isotopes and many more can be made in the laboratory.

Basically, isotopes of an element are all the same element (they have the same number of protons) but they have different masses. The chemical properties of all the isotopes of an element will be the same but their physical properties will be different because of their different masses. This means that properties like the boiling point and density of isotopes of an element will be different. For example 'heavy water' containing the isotope of hydrogen 2 1H (called deuterium) has a boiling point of 104 oC. Radioactive isotopes (with different half lives) are used for a variety of purposes – see the section on half-life.

A few other isotopes of some of the elements are shown in the table below.

Carbon 14 (6 protons and 8 neutrons) and carbon 12 (6 protons and 6 neutrons) are two isotopes of carbon.
Radioactive isotopes (radio isotopes) are ones that are radioactive and emit either alpha, beta or gamma radiation. These are used for a variety of purposes in medicine and industry.