Science
Subatomic particles.
Definition
The particles that make up an atom: protons (positive charge, in the nucleus), neutrons (no charge, in the nucleus), and electrons (negative charge, orbiting the nucleus). The number of protons defines the element, while changes in neutrons or electrons create isotopes or ions.
Examples
Real-world.
- 1 A carbon-12 atom has 6 protons, 6 neutrons, and 6 electrons
- 2 Removing an electron from sodium creates a Na⁺ ion with a positive charge
- 3 Carbon-14 has 2 extra neutrons compared to carbon-12, making it radioactive and useful for dating
Key Fact
Proton mass ≈ neutron mass ≈ 1 amu; electron mass ≈ 1/1836 amu. Atomic number = number of protons.