C4- Development of the atomic theory

developed an atomic theory in the 1800s

he described atoms as solid spheres. different ones are made up of different elements.

his conclusions:

• all matter is made of atoms
• atoms cannot be broken down into anything simpler
• in a chemical reaction, atoms are rearranged
• all atoms of the same element are the same
• compunds form when two or more different atoms join

HIS THEORY WAS DEVELOPED BY MANY OTHER SCIENTISTS

discovered te electron in 1897

showed Dalton was wrog. Made Plum pudding model

the atom was imagined as a sphere of positive charge with negatively charged electrons dotted around inside, rather like plums in a pudding. An experiment was carried out in 1905 to support this 'plum pudding' model of the atom

• dalton thought atoms couldnt be simplified
• Thompson used measurements of charge and mass to prove electrons existed

discovered the atom contained a nucleus in 1911

he found:

• more evidence that showed the atom contained smalle pieces
• thought most of the atom was empty space

GOLD FOIL EXPERIMENT

WHAT HAPPENED:

• Rutherford tested plum pudding model
• fired alpha particles at thin gold foil
• they expected particles to pass straight through
• some particles emerged at different angles and some cam straight back. this showed the positive alpha particles were being repelled by the positive nucleus .

PROVED PLUM PUDDING MODEL WRONG

supported Rutherfords atom model

showed electrons contained in shells

each shell had a fixed energy