This key facts covers The Three Subatomic Particles within Atomic Structure for GCSE Chemistry. Revise Atomic Structure in Atomic Structure for GCSE Chemistry with 28 exam-style questions and 22 flashcards. This topic appears regularly enough that it should still be part of a steady revision cycle. It is section 5 of 14 in this topic. Use this key facts to connect the idea to the wider topic before moving on to questions and 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.
Practice questions for Atomic Structure
What does the atomic number of an element tell you?
Explain what is meant by the relative atomic mass of an element and how it is calculated from isotopic data. [3 marks]