State the relative charges and relative masses of a proton, a neutron and an electron

Atoms, Elements and Compounds – Atomic Structure & Periodic Table

Objective

State the relative charges and relative masses of a proton, a neutron and an electron. ⚛️

What are the tiny building blocks?

Think of an atom as a tiny solar system:

• 🌞 The nucleus is the bright sun – it contains protons (positive) and neutrons (neutral).
• 🌑 The electrons are tiny moons that orbit far away, carrying a negative charge.
• ⚖️ The mass of the atom is almost entirely in the nucleus; electrons are almost massless.

Charges – How do they compare?

The elementary charge $e$ is the basic unit of electric charge.

• Proton: $+1\,e$ (positive)
• Electron: $-1\,e$ (negative)
• Neutron: $0\,e$ (neutral)

Masses – How big are they?

Mass is measured in atomic mass units (amu).

• Proton: $1.0073\,\text{amu}$
• Neutron: $1.0087\,\text{amu}$
• Electron: $0.0005\,\text{amu}$ (almost nothing!)

Quick Reference Table

Exam Tips

1. Write the charge of a proton as $+1\,e$, electron as $-1\,e$, neutron as $0\,e$.
2. Remember the relative mass of an electron is negligible – it can be omitted when calculating atomic mass.
3. Proton and neutron masses are both about 1 amu; the neutron is slightly heavier.
4. Use the table to quickly check values during revision.
5. Practice converting between charge units and mass units in past exam questions.