The changing atom

?
Fifth century BCE- the Greek atom.
Greek philosopher Democritus developed 1st idea of atom.
Can only divide sample of matter certain amount of times.
Indivisible particle= atomos.
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Early 1800s- Dalton's atomic theory.
Atoms= tiny particles that make up elements.
Atoms can't be divided.
All atoms of an element are the same.
Atoms of one element= different to those of other elements.
Developed the 1st table of atomic masses.
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1897-1906 - J.J. Thomson -Discovered electrons.
PLUM PUDDING
-Discovered that cathode rays= a stream of particles with the following properties: -ve charge;
could be deflected by both magnet + electric field.; very small mass
-Concluded: e- came from within the atoms of the electrodes.
-Atoms = made up of-ve e-s mo
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1909-11 - Ernest Rutherford's gold-leaf experiment. NUCLEAR ATOM
Directed a-particles towards a sheet of very thin gold foil.
Measured deflection of the particles.
Most particles weren't deflected back to source, but some were.
+ve charge of atom=concn in a nucleus at centre.
- The -ve e- orbit the nucleus.
- Most of v
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1913- Niels Bohr's planetary model + Henry Moseley's work on atomic numbers.
- e- orbited a central nuclear sun in shells.
Model helped explain: Spectral lines seen in emission spectra; the energy of e- at diff distances from nucleus.

Moseley discovered link between X-ray frequencies + an elements atomic number.
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1918- Rutherford discovers the proton.
- Explained Moseley's finding that an atom's atomic number was linked to X-ray frequencies.

-The atomic number= the number of protons in an element's atom.
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1923-26 - Wave and Particle behaviour.
1923: Louis de Broglie suggested that particles could have the nature of both wave + particle.

1926: Austrian physicist Erwin Schrodinger suggested that an e- had wave like properties in an atom. + He introduced the idea of atomic orbitals.
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1932- James Chadwick discovers the neutron
Observed a new type of radiation emitted from some elements.
Radiation = made up of uncharged particles with approximately the same mass as a proton.
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Modern day
Thought that protons and neutrons are made up of even smaller particles (quarks).
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Other cards in this set

Card 2

Front

Early 1800s- Dalton's atomic theory.

Back

Atoms= tiny particles that make up elements.
Atoms can't be divided.
All atoms of an element are the same.
Atoms of one element= different to those of other elements.
Developed the 1st table of atomic masses.

Card 3

Front

1897-1906 - J.J. Thomson -Discovered electrons.
PLUM PUDDING

Back

Preview of the front of card 3

Card 4

Front

1909-11 - Ernest Rutherford's gold-leaf experiment. NUCLEAR ATOM

Back

Preview of the front of card 4

Card 5

Front

1913- Niels Bohr's planetary model + Henry Moseley's work on atomic numbers.

Back

Preview of the front of card 5
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