Isotopes Review


Isotopes - Atoms with the same number of protons, but a different number of neutrons (same element, different isotopic mass)

Example: Carbon can exist the isotopes carbon-12, carbon-13, and carbon-14. They both have 6 protons (or else they wouldn't be carbon), but a different number of neutrons.

Isotope	Protons	Neutrons	Calculating
126C	6	6	You calculate the neutrons by subtracting the bottom number (atomic number) from the top number (isotopic mass). So for carbon-13:                 13 (#protons & neutrons)                 -6 (#protons)                  7 (#neutrons)
136C	6	7
146C	6	8

The atomic mass that appears on the periodic table is a weighted average of all of the isotopes that are known to exist.