Involves

Word

Isotope

EYE-suh-tohp · noun

An atomic form of an element with the same proton count but a different neutron count from another form

Examples

  • Carbon-14 is an isotope of carbon, as are carbon-12 and carbon-13.

  • Changing an atom's isotope changes its neutron count; changing its element changes its proton count.

Origin

The name refers to occupying the same place in the periodic table. Frederick Soddy introduced the isotope concept in 1913 to account for forms with different atomic weights but essentially the same chemical behavior. The later neutron-based explanation made the distinction inside the nucleus clear.

How it connects

Isotope names a difference within one elemental identity.

This word appeared in The same element with a different nucleus, the Involves connection for September 29, 2026, which asked: What can change inside an atom without changing which element it is?

Check yourself

Two atoms have six protons each, but different neutron counts. What are they?

Different isotopes of carbon. Exactly. The shared proton count fixes carbon; differing neutron counts distinguish isotopes.

What the sources establish

  • Isotopes share proton number but differ in neutron number; Soddy formulated the concept in 1913.

Sources