models of atomic [blank_start]structure[blank_end] have changed slightly over the years...
in the start of the [blank_start]19th[blank_end] century, [blank_start]john Dalton[blank_end] described atoms as [blank_start]solid spheres[blank_end]... he said that these [blank_start]spheres[blank_end] made up different elements.
in [blank_start]1897[blank_end], [blank_start]J.J.Thompson[blank_end] discovered the [blank_start]electron[blank_end]. this showed that atoms couldn't be solid spheres and indivisible. the new model was known as the [blank_start]plum pudding model[blank_end].
in [blank_start]1909[blank_end], [blank_start]Ernest Rutherford[blank_end] and his students conducted the [blank_start]gold foil experiment[blank_end] where they fired [blank_start]alpha[blank_end] particles at a very thin [blank_start]gold[blank_end] sheet. the plum pudding model suggested that [blank_start]most[blank_end] alpha particles would be slightly [blank_start]deflected,[blank_end] however most particles passed straight through with only a few being deflected. this showed that the plum pudding model was [blank_start]wrong[blank_end]. [blank_start]Rutherford[blank_end] developed the [blank_start]nuclear model[blank_end]. this showed a tiny [blank_start]positive[blank_end] nucleus, surrounded by a [blank_start]cloud[blank_end] of negative electrons, with most being [blank_start]empty space[blank_end].
scientists realised that if electrons where in a cloud then they would [blank_start]spiral[blank_end] down and cause the atom to [blank_start]collapse[blank_end]. [blank_start]Niels Bohr[blank_end] proposed a new model where electrons exist in shells or orbits of [blank_start]fixed energy[blank_end]. when electrons move between shells, [blank_start]electromagnetic radiation[blank_end] is absorbed or emitted. this model fitted experimental observations.
this model is still used even though we can refine it into [blank_start]sub-shells[blank_end] as this model is simple and easy to understand.
plum pudding model
gold foil model
apple pudding model
'gold foil experiment'
'plum pudding experiement'
'alpha particle experiment'
plum pudding extended model
plenty of space
p and s shells
who described electrons as solid spheres and in when? [blank_start]John Dalton[blank_end] and in [blank_start]the 19th centrury[blank_end].
the 19th centrury
in 1892, jj. Thompson made the plum pudding model.
put the scientists in order with their year and experiment...
[blank_start]John Dalton[blank_end] [blank_start]described atoms as solid spheres[blank_end] in [blank_start]the 19th century[blank_end].
[blank_start]ernest Rutherford[blank_end] [blank_start]conducted the gold foil experiment[blank_end] in [blank_start]1897.[blank_end]
[blank_start]Niels bohr[blank_end] [blank_start]discovered shells and orbits[blank_end] of [blank_start]fixed energy[blank_end].
scientists later refined this to have [blank_start]sub-shells[blank_end].