The Atom

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