History Of The Atom Flashcards
Key ideas of the atom have been proposed by …
Dalton
Thompson
Rutherford
Bohr
Who were the first to have ideas about the atom?
Ancient Greeks
What did Dalton figure from his experiments?
Substances were made up of atoms which were tiny and hard shaped like spheres.
Each chemical element had its own atoms that differed from others in mass.
Atoms could not be divided or split.
Atoms rearranged themselves in chemical reactions.
Why are daltons ideas still useful today?
They help to visualise elements, compounds and molecules.
What year did dalton make his discoveries ?
1803
What year did Thompson make his discoveries?
1897
What was the main thing that Thompson discovered?
The electron
How did Thompson discover the electron?
Bonus question ! - how did he do the experiment ?
He did experiments on the beams of particles and found they that were attracted to a positive charge showing that they must be negatively charged.
Bonus ! - he experimented by applying high voltages to gases at low pressure.
Which scientist proposed the plum pudding model ?
JJ Thompson
Explain the plum pudding model of an atom
This model suggested that the tiny electrons must be embedded in a cloud of positive charge.
The positive charge being the sponge and the electrons being the bits of plum in a plum pudding.
Why did Daltons idea of atoms being unable to split or divide have to be revised?
Thompson noticed during his experiment that the electrons he discovered had to have come from inside the tube he was experimenting with meaning that they must have split from the atoms inside the tube.
Who made discoveries in 1911
Rutherford
Who carried out Rutherfords experiments under his directions ?
His university students Geiger and marsden
What was the most important thing that Rutherford discovered?
Nucleus
What was the atomic model called proposed by Rutherford ?
Nuclear model
In his experiment Rutherford discovered that atoms could not have a diffused cloud of p_____ c____ because they wouldn’t r_____ when hitting the sheet of g___
In his experiment Rutherford discovered that atoms could not have a diffused cloud of POSITIVE CHARGE because they wouldn’t REPELL when hitting the sheet of GOLD
Rutherford proposed that the positive charge must be ….
Concentrated in a tiny spot in the centre of the atom
Where did Rutherford suggest the electrons were oppose to being embedded in a cloud of positive charge
Orbiting around the nucleus
Who made discoveries in 1914
Niels Bohr
What did Bohr notice about atoms when they were heated?
They gave out light which had specific amounts of energy
What did Bohr suggest about the electrons which orbited the nucleus ?
That they were orbiting the nucleus at set distances in energy levels (shells)
What did Bohr suggest that happens when energy is given out of an atom?
Energy must be given out when excited electrons fall from a high to a low energy level.
Who did an experiment that could only be explained by the existence of neutrons ?
What year was this ?
James Chadwick 1932
Why did scientists at the time speculate that there was a second sub-atomic particle atom inside of the nucleus ?
It explained the missing madd that had been noticed in atoms
What two sub-atomic particles are inside of the nucleus ?
Protons and neutrons
Name the 3 sub-Atomic particles
Electrons
Protons
Neutrons
Why is it hard to detect neutrons in experiments ??
They carry no charge
