Atomic structure

Question 1

Dalton’s Atomic structure

Answer 1

1. All matter is made up of small, identical particles called atoms.
2. Atoms are indivisible (cannot be broken down into simpler particles).
3. Atoms cannot be created or destroyed.

Question 2

William Crookes

Answer 2

Cathode ray tube & Paddle wheel
-Cathode ray moves from cathode to anode (Maltese cross) through vacuum, causing glass to fluoresce, leaving shadow of cross.
Cathode rays:
1. Move in straight lines from the cathode to the anode
2. Have sufficient energy to move the paddle wheel
3. Cause glass to fluoresce

Question 3

J.J. Thompson

Answer 3

• Discovered the electron (fired cathode rays between oppositely charged plates).
• Calculated the e/m ratio.
• Plum pudding model (negatively charged electrons embedded in positively charged sphere)

Question 4

George Stoney

Answer 4

Named the electron

Question 5

Robert Millikan

Answer 5

• Oil drop experiment
• Calculated the charge and mass of the electron (using the e/m ratio)

Question 6

Ernest Rutherford

Answer 6

• Gold Foil Experiment (fired alpha particles through a thin sheet of gold foil surrounded by detectors)
  
  1. Atoms are mostly empty space (most alpha particles moved straight through).
  2. Atoms have a positively charged nucleus (some particles deflected at wide angles).
  3. The nucleus is dense (some particles deflected straight back).
• Discovered protons (positive particles released from substances bombarded with alpha particles)
• New atomic model (protons in nucleus surrounded by electron cloud)

Question 7

James Chadwick

Answer 7

Discovered the neutron (neutral particles released by substances bombarded by alpha particles)