Main ideas
Hunters and gatherers - heat treated wood of their spears - noticed hardening
Cooks - made compounds - first chemists
metalurgists - in stone age
Wizards - collected herbs and poisons
Alchemists - wanted to urn lead into gold

All of these were the precursors to modern scientists and chemists in particular
they observed, hypothesised, and tested the hypotheses and from there came up with theoris about how the world worked.
Famous chemists
Priestly discovered oxygen
Lavoisier - the law of conservation of mass
Dalton - that atoms existed as hard indivisible balls and each was different to others and hence elements were identified Tried to weigh them to determine differences.
Mendeleev - arranged known elements in order of weight. - the first periodic table

Upto now no idea of protons neutrons and electrons
The history of the structure of the atom is as follows
1804- Dalton - hard balls
1897 Thomson - plumb pudding model - some positives in there with some negatives
1911Rutherford nucleus of positives and electrons orbiting
1913 Bohr - distinct shells for electrons and energy levels - Flame tests
1926 Schrodinger - approximate position of electrons - uncertainty principle
1932 Chadwick - neutrons