OCR Chemistry 1.1.1 Atoms & Reactions

Atoms & Reactions 1.1.1

relative charge relative mass

proton +1 1

neutron 0 1

electron -1 1/2000

All three sub-atomic particles act differently in an electric field. The neutron is unaffected as it has no charge so it passes staight on. The proton is attracted towards the negative plate as it is positively charged. The electron is attracted towards the positive plate, however is deflected more prominently as it has a much lower mass than the proton.

• Greeks - all matter is made up of tiny particles. If you were to repeatedly divide matter there would become a point where it could not be divided any further
• Dalton - atoms in any element are all of the same kind; a compound contains 2 or more elements combined in fixed proportions (this was accepted at the time); during chemical reactions, atoms in the reactants rearrange to form the reactants in the products
• Thompson - found the electron; knew that the atom must be neutral therefore part is +ve and part is -ve; plum pudding model (this was accepted at the time)
• Rutherford - fired alpha particles at gold foil, knew they were positively charged but they surprisingly went straight through the gold foil and a few bounced straight back; found the proton; said that the proton did not account for the whole mass…