This key facts covers The Three Subatomic Particles 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 5 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 5 of 13
Practice
25 questions
Recall
22 flashcards
📌 The Three Subatomic Particles
Every atom is made of three types of particle:
- Protons — Found in the nucleus. Relative mass = 1. Relative charge = +1. The number of protons defines the element!
- Neutrons — Found in the nucleus. Relative mass = 1. Relative charge = 0. They add mass but no charge.
- Electrons — Found in shells around the nucleus. Relative mass = 1/1836 (effectively 0). Relative charge = -1.
The nucleus:
- Contains protons and neutrons (together called nucleons)
- Very small compared to the atom — but contains 99.9% of the mass
- Has an overall positive charge (because of the protons)
Key principle: In a neutral atom, the number of protons EQUALS the number of electrons. This balances the charges (positive cancels negative).
Quick Check: A sodium atom has atomic number 11 and mass number 23. How many neutrons does it have?
12 neutrons. Neutrons = mass number − atomic number = 23 − 11 = 12.