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The Atom flashcards
John Dalton’s Atomic Theory
All matter is made up of very small particles called atoms
All atoms are indivisible
Atoms cannot be created or destroyed
Cathode Rays
Cathode rays are streams of negatively charged particles called electrons
William Crooke’s experiments
Maltese cross experiment and paddle wheel experiment
William Crookes conclusions
Cathode rays travel in straight lines
Cathode rays cause glass to fluoresce
Cathode rays have enough energy to move a
JJ Thompson’s Plum Pudding model
Thompson proposed an atom as a sphere of positive charge with negative electrons embedded in it t random
Conclusion of JJ Thompson’s experiment
Cathode rays consist of negatively charged particles called electrons
Milikans experiment
Oil drop experiment
Charge on the electron
1.6×10-19 Coulombs
Alpha particles
2 protons + 2 neutrons
Observation: Most particles passed straight through
Conclusion: Atom is mostly empty space
Observation: Some deflected at slight angles
Conclusion: Small positive nucleus
Observation: Few reflected back
Conclusion: Nucleus is dense
Proton’s relative charge
+1
Proton’s relative mass
1
Proton’s location
Nucleus
Neutron’s relative charge
0
Neutron’s relative mass
1
Neutron’s location
Nucleus
Electron’s relative charge
-1
Electron’s relative mass
1/1838
Electron’s location
Outside nucleus
Ernest' Rutheford’s experiment
Bombarded gold foil with alpha particles
James Chadwick’s experiment
Bombarded berryllium with alpha particles
Note
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