Isotopes
Simple Explanation
Isotopes are atoms of the same element (same number of protons, and therefore the same chemical properties) that have different numbers of neutrons — and therefore different atomic masses. Some isotopes are stable; others are radioactive (unstable) and decay over time.
Why Do We Need It?
Isotopes have important applications in medicine (radioactive tracers and treatments), archaeology and geology (radiometric dating), and energy production (nuclear power), among many other fields.
Why Does This Work?
Since chemical behaviour is determined almost entirely by the number of protons (and therefore electrons) an atom has, isotopes of the same element behave nearly identically in chemical reactions — but the different number of neutrons changes the nucleus's mass and, for some combinations, its stability, which is why some isotopes are radioactive while others (with a more stable proton-to-neutron ratio) are not.
Real-Life Example
Carbon dating
Archaeologists estimate the age of ancient organic remains using carbon dating.
Carbon-14, a radioactive isotope of carbon, decays at a known, constant rate — by measuring how much carbon-14 remains in a sample compared to the stable isotope carbon-12, scientists can estimate how long ago the organism died.
Practice
What distinguishes different isotopes of the same element?
EasyCommon mistake
Thinking isotopes of an element behave very differently chemically — since chemical behaviour depends almost entirely on proton/electron number (which is identical across isotopes of the same element), isotopes behave nearly identically in chemical reactions; only their nuclear properties (mass, stability, radioactivity) differ.
Quick Review
- Isotopes: same element (same protons), different numbers of neutrons.
- Isotopes have nearly identical chemical behaviour but can differ in nuclear stability.
- Applications: radiometric dating, medical tracers, nuclear energy.