Isotopes: Same Element but with Different Masses

• Isotopes are elements whose atoms differ in mass due to varying numbers of neutrons.
• They are the same element because they have the same number of protons (atomic number).
• They are chemically identical.
• Isotopes are identified by their mass numbers.
• Protons + neutrons = mass number

• Isotopic symbol

13

Al

26.981

Atomic number, Z

Atom symbol

Atomic weight