Cambridge IGCSE Physics 0625 – 5.1.2 The nucleus5.1.2 The nucleus
Learning Objective
State the relative charges of protons, neutrons and electrons as \$+1\$, \$0\$ and \$-1\$ respectively.
Key Concepts
- Atoms consist of a tiny, dense nucleus surrounded by electrons.
- The nucleus contains protons and neutrons.
- Protons carry a positive charge, neutrons are neutral, and electrons carry a negative charge.
Particle Charge Table
| Particle | Symbol | Relative Charge |
|---|
| Proton | \$p^{+}\$ | \$+1\$ |
| Neutron | \$n^{0}\$ | \$0\$ |
| Electron | \$e^{-}\$ | \$-1\$ |
Why the Charges Matter
The sum of the charges of all particles in an atom determines its overall electrical neutrality. For a neutral atom:
\$\text{Total charge} = (\text{Number of protons})\times(+1) + (\text{Number of electrons})\times(-1) = 0\$
Since neutrons have no charge, they do not affect the charge balance.
Common Misconceptions
- Thinking that neutrons have a small negative charge – they are truly neutral.
- Assuming the magnitude of the electron charge is different from that of the proton – both have equal magnitude, opposite sign.
- Confusing the symbol \$e\$ for the electron with the elementary charge \$e\$ (approximately \$1.602\times10^{-19}\,\text{C}\$).
Check Your Understanding
- What is the relative charge of a proton? Answer: \$+1\$.
- What is the relative charge of a neutron? Answer: \$0\$.
- What is the relative charge of an electron? Answer: \$-1\$.
- If an atom has 12 protons and 12 electrons, what is its net charge? Answer: \$0\$ (neutral).
Suggested diagram: A simple schematic of an atom showing a central nucleus with protons (+) and neutrons (0) and electrons (–) in orbitals.