Isotopes — Same Element, Different Mass
Part of Atomic Structure — GCSE Chemistry
This key facts covers Isotopes — Same Element, Different Mass within Atomic Structure for GCSE Chemistry. Revise Atomic Structure in Atomic Structure for GCSE Chemistry with 25 exam-style questions and 22 flashcards. This topic appears less often, but it can still be a useful differentiator on mixed-topic papers. It is section 7 of 13 in this topic. Use this key facts to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 7 of 13
Practice
25 questions
Recall
22 flashcards
⚗️ Isotopes — Same Element, Different Mass
Definition: Isotopes are atoms of the same element (same number of protons) but with different numbers of neutrons.
Why this matters:
- Same element = same chemical properties (because they have the same electrons)
- Different mass = different physical properties (density, rate of diffusion)
- Some isotopes are radioactive (unstable nuclei that decay)
Example — Carbon isotopes:
- Carbon-12 (⁶¹²C) — 6 protons, 6 neutrons — most common, stable
- Carbon-13 (⁶¹³C) — 6 protons, 7 neutrons — stable, used in NMR
- Carbon-14 (⁶¹⁴C) — 6 protons, 8 neutrons — radioactive, used in carbon dating
Quick Check: Two atoms have atomic number 6 but one has mass number 12 and the other has mass number 14. What is the relationship between these atoms?
They are isotopes of carbon. Both have 6 protons (same element) but different numbers of neutrons (6 and 8 respectively), giving different mass numbers.