Chemistry C3 AQA GCSE

Dalton: order of mass
Newlands: 'law of octaves'; assumed all elements found- shoved them in anywhere and ignored patterns
Mendeleev: order of atomic mass- pattern imerged; left gaps for undiscovered

Now:
- organised in atomic number (proton number)
- REACVTIVITY
   - larger atoms lose electons more easily and gain them less easily.
   - Group 1- reactivity increases going down the group- more shielding :)
   - Group 7- reactivity decreases going down the group- more shielding :(