Skip to content

Help Zone

Student Question

Secondary IV • 9mo.

Hello! I'm not sure I understand why isotopes change the atomic mass of an atom ... Can you help me? Thank you very much in advance!


{t c="richEditor.description.title"} {t c="richEditor.description.paragraphMenu"} {t c="richEditor.description.inlineMenu"} {t c="richEditor.description.embed"}

Explanations (1)

  • Explanation from Alloprof

    Explanation from Alloprof

    This Explanation was submitted by a member of the Alloprof team.

    Team Alloprof • 9mo.


    The atomic mass of an atom is determined by the sum of the mass of the protons and neutrons it contains. Electrons have a mass which is much smaller relative to the components of the nucleus, so its mass is not considered.

    Since atomic mass depends on the number of neutrons, and this tends to vary with different isotopes of an atom, then different isotopes will have different masses.

    In the periodic table, we can observe the relative atomic mass of the elements which is weighted according to the mass of the different isotopes and their frequency in nature.

    I hope that this answers your question. Don't hesitate to ask other questions! :)