Seven short lessons, in order. Each ends with a check. You can open any of them — the sequence is the recommended walk, not a lock.
- 1
Lesson 1
Protons
A proton has charge +1. The proton count is the atomic number — it is the element.
- 2
Lesson 2
Neutrons
Neutrons add mass but not charge. Change them and the element stays the same.
- 3
Lesson 3
Electrons
Electrons occupy shells. They are the particles that make and break bonds.
- 4
Lesson 4
Isotopes
Same proton count, different neutron count. Carbon-12 and carbon-14 are both carbon.
- 5
Lesson 5
Element identity
Change the proton count and you change the element. Nothing else does that.
- 6
Lesson 6
The periodic table
Rows are periods (shells filling). Columns are groups (shared valence behavior).
- 7
Lesson 7
Atoms to molecules
Atoms share or transfer electrons. H wants 1 bond, O wants 2, C wants 4.