chemistry - development of periodic table

how did it all start ?

johann wolfgang dobreiner : discovered that similar elements came in trios (e.g lithium, sodium, potassium)

how were the elements ordered after this, and by who ?

john newlands : law of octaves = every 8 elements were similar in terms of reaction; ordered in terms of increasing atomic weight

what was the problem with the law of octaves ?

by sticking to exact order of atomic weight, elements w/ completely different properties were grouped together

who came famously after that, and what did he do ?

dmitri mendeleev : grouped elements in terms of increasing atomic weight (protons and therefore atomic number = not yet discovered) but also organised them so they’d fit patterns of other elements in the same group.

also left space for undiscovered elements, and predicted what they’d be like based on properties of other elements in the same group.