Some important terms which you must know are:
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Atomic number (Z) - the number of protons in the nucleus. This number is characteristic of a given element.
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Atomic mass number (A) - the sum of the protons and neutrons in a given atom (p + n).
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Atomic mass - the actual mass of an average atom in a sample. The characteristic atomic masses for Earth are shown on periodic tables.
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Atomic Mass Unit: the atomic mass unit = amu is a unit of mass for atoms. It is defined as 1/12 the mass of one atom of 12C, where the mass of 12C is defined as 12 exactly.
| Symbol |
Z |
A |
p |
n |
e- |
| 14C |
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| 238U6+ |
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| 35Cl- |
|
|
|
|
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| 18O2- |
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© R A Paselk
Last modified 31 Janaury 2011