ISOTOPES

=Isotopes= Isotopes are versions of an element with a different numbers of neutrons [image:http://i.imgur.com/yHSdXdf.png?1] Atoms of a given element always have the same number of protons. However, they can have different numbers of neutrons. For instance these three isotopes (versions) of carbon have a different number of neutrons. Carbon-12 has 6 neutrons Carbon-13 has 7 neutrons Carbon-14 has 8 neutrons The atomic number of an element always identifies a specific element. The number of both protons and neutrons (total) in the nucleus is the atom's mass number. Because isotopes have different numbers of neutrons the mass number is different for each. [image:http://i.imgur.com/yWyxVQt.png?1] The mass number on most periodic tables usually indicates the most common isotope or is based on the average number of neutrons. This is why the mass number isn't always a whole numbers. For instance Chlorine has an atomic mass of approx 35.45 Chlorine always has 17 protons, but around 75% of chlorine atoms have 18 neutrons and around 25% of them have 20 neutrons. Therefore the atomic mass is roughly 35.5