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The Professional Development Service for Teachers is funded by the Department of Education and Skills under the National Development Plan Rutherfords Gold.

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Presentation on theme: "The Professional Development Service for Teachers is funded by the Department of Education and Skills under the National Development Plan Rutherfords Gold."— Presentation transcript:

1 The Professional Development Service for Teachers is funded by the Department of Education and Skills under the National Development Plan Rutherfords Gold Foil Experiment T.T.

2 PDST Resources for Leaving Certificate Physics 2 Rutherfords gold-foil experiment The atom is a solid sphere It contains negative electrons Positive material Negative electrons This was called the Plum Pudding Model Before this experiment, we assumed that: Electrons were compared to fruit, positive material to cake

3 PDST Resources for Leaving Certificate Physics 3 97 % % <1 % Ra Rutherford fired α-particles at gold foil He knew α-particles were small, fast moving and positive 97% went straight through 2-3% were deflected Less than 1% bounced back LiS movable Lithium sulphide detector Rutherfords gold-foil experiment

4 PDST Resources for Leaving Certificate Physics 4 97 % % <1 % Ra LiS movable Lithium sulphide detector The key result is the 1% that bounce back Rutherford compared the experiment to firing artillery shells at tissue paper Why would any bounce back? Rutherfords gold-foil experiment

5 PDST Resources for Leaving Certificate Physics He concluded that: 97% pass through because they are meeting nothing Those deflected are coming close to a positive charge Those that bounce back are heading straight for a positive charge 97% 2-3% 1% The atom is mainly empty space, with a small area of positive charge Rutherfords gold-foil experiment

6 PDST Resources for Leaving Certificate Physics 6 Conclusions The atom is mainly empty space There is a small area of positive charge at the centre (the nucleus) + nucleus electrons The Rutherford – Bohr Model of the Atom (as studied at junior cert.)

7 PDST Resources for Leaving Certificate Physics 7 Atomic number The number of protons Mass number The total number of protons and neutrons All elements have an atomic and mass number e.g. for Lithium: 3p 4n


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