Relative Charge
Summary: The electric charge of a subatomic particle expressed relative to the charge of a proton, which is taken as +1. Tags: igcse chemistry keyword Created: 2026-08-06
Relative charge compares the electric charge of a particle to the charge of a proton, which is taken as the standard of +1. Because actual charges in coulombs are extremely small, chemists use relative values that are simple whole numbers. The values for the three subatomic particles are:
- Proton: relative charge +1
- Neutron: relative charge 0
- Electron: relative charge −1
The key IGCSE exam point is using relative charges (and relative masses) to work out the structure of atoms and ions. Since a neutral atom has equal numbers of protons and electrons, its overall charge is zero. When an atom loses electrons it becomes a positive ion (more protons than electrons), and when it gains electrons it becomes a negative ion (more electrons than protons). For example, an oxygen ion with 8 protons and 10 electrons has a charge of 8 − 10 = −2 (O²⁻).
Sources
- Cambridge IGCSE Chemistry 0620 Syllabus (2023-2025), Cambridge Assessment International Education
Common Misconceptions
| Misconception | Reality |
|---|---|
| Neutrons have a small negative charge | Neutrons have no charge at all — relative charge 0 |
| Electrons have a charge of −1.6 × 10⁻¹⁹ C at IGCSE level | IGCSE uses relative charge: −1 for the electron, +1 for the proton |
| The charge on an ion tells you its mass | Charge and mass are separate properties; ions of the same element have the same mass but can differ in charge |