This how it works covers How It Works: Why Some Nuclei Are Unstable within Atomic Structure for GCSE Physics. Revise Atomic Structure in Atomic Structure for GCSE Physics with 16 exam-style questions and 25 flashcards. This topic appears less often, but it can still be a useful differentiator on mixed-topic papers. It is section 6 of 12 in this topic. Use this how it works to connect the idea to the wider topic before moving on to questions and flashcards.
⚙️ How It Works: Why Some Nuclei Are Unstable
The nucleus is held together by the strong nuclear force — a force that acts between protons and neutrons at extremely short range. This force is much stronger than the electromagnetic repulsion between protons, but it only operates over very short distances.
When the ratio of neutrons to protons is wrong — too many or too few neutrons — the nucleus becomes unstable. An unstable nucleus will spontaneously emit radiation to achieve a more stable configuration. This is the basis of all radioactivity.
Small nuclei (up to calcium) are most stable with roughly equal numbers of protons and neutrons. Large nuclei need more neutrons than protons to provide enough binding force to overcome the greater electrostatic repulsion between many protons.
Practice questions for Atomic Structure
What does the atomic number of an element tell you?
Describe the structure of an atom. Include the location and charge of the three main subatomic particles.