Glossary

Plain words, in the order you meet them.

Atom
Smallest bit of an element; protons + neutrons in the middle, electrons outside.Met at stop 2 · Atoms
Element
One kind of atom (oxygen, iron).Met at stop 2 · Atoms
Compound
Joined elements in fixed ratio (water).Met at stop 4 · Bonding
Mole
6.02×10²³ particles — the chemist's counting heap.Met at stop 5 · Moles
Molarity
Moles per litre of solution.Met at stop 9 · Solutions
Ion
Charged atom (lost or gained electrons).Met at stop 2 · Atoms
Isotope
Same element, different neutrons.Met at stop 2 · Atoms
pH
The 0–14 acidity scale.Met at stop 10 · Acids & bases
Catalyst
Speeds a reaction without being used up.Met at stop 11 · Energy & rates
Polymer
Long chain of repeats (plastics, starch).Met at stop 12 · Carbon