What is an isotope?

An atom of an element with a different number of neutrons.

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  1. A molecule with extra electrons
  2. An atom of an element with a different number of neutrons ✔
  3. An atom with a different number of protons

Why: Isotopes of an element share proton number but differ in neutron number, changing mass number.

Huh, didn't know that: Isotopes of an element share proton number but differ in neutron number, changing mass number.

The dad joke
Isotopes are element siblings with different neutron counts.
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References

Answer: An atom of an element with a different number of neutrons. Isotopes of an element share proton number but differ in neutron number, changing mass number.

  1. Scouting America: Nuclear Science www.scouting.org/merit-badges/nuclear-science
    Construct 3-D models for the atoms of three isotopes of this element
    Checked 2026-11-07.

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