They are variations of chemical elements, such as Carbon-12 vs. Carbon-14. Although each element has the same number of protons (atomic number), they can have differing numbers of neutrons, and therefore different (atomic masses). Isotopes of any particular element can have different properties, and be more or less stable than others.
- Main Article: Atomic mass
The atomic mass of an element is the average mass of the isotopes of that element.. The atomic mass of any specific atom (or isotope) is a combination of the number of protons plus the number of neutrons it possesses. For example, carbon always has 6 protons and typically also has 6 neutrons, but some carbons have 7 neutrons, and a trace amount of carbon can be found with 8 neutrons. These variations of carbon atoms are what are known of as isotopes.
The atomic mass and thus the isotope a particular element is abbreviated with a superscript above the elemental symbol, such as 12C, 13C, and 14C. Alternatively, the isotope can be written in a hyphenated form such as Carbon-12 or C-12.
The atomic mass listed for each element in the Periodic Table of Elements is the average atomic mass of the various isotopes found in nature.
|Carbon-12||6 Protons + 6 Neutrons|
|Carbon-13||6 Protons + 7 Neutrons|
|Carbon-14||6 Protons + 8 Neutrons|
- Cox, H., Porch, T., Wetzel, J. Chemistry for Christian Schools. Bob Jones University Press; Greenville, South Carolina. 2000 (p.534).
- Cox, p.529
- Isotopes University of Colorado