What is an isotope?
Isotopes are atoms of the same element with the same proton number but different numbers of neutrons.
How it works and what the evidence shows
Core idea Proton count defines the element, while neutron differences alter mass number. Oxygen-16 and oxygen-18 are isotopes of oxygen. Some isotopes are stable and some radioactive. Evidence and research Isotope ratios can trace water origins, environmental processes and geological records. Radioactive decay rates can support dating under appropriate conditions.
Uses and limitations
Why it matters Isotopes matter in chemistry, environmental science and nuclear physics. Sample origins, standards, mixing and fractionation need consideration. Common misunderstandings An isotope is not necessarily radioactive; many are stable. A neutron difference does not create a different element.