Chapter 2 - Atoms Flashcards

1
Q

Who said matter was made up of small particles

A

Greek philosophers

Democritus was one

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2
Q

How was the Electron discovered

A

Passed electric currents (cathode rays) through a glass tube (vacuum tube) containing air at low pressure
• Crookes Rays
• Radiation was coming from metal plate (cathode)
• Shadow of Maltese cross
• Cause glass to fluoresce

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3
Q

Crookes Paddle Wheel

A

Investigate property of cathode rays

Vanes always turned away from cathode

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4
Q

J.J Thompson

A
  • Proved cathode rays consisted of negatively charged particles
  • Cathode rays attracted to positive beam of light
  • Caused fluorescent screen to glow

• High voltage is dragging electrons out of the atoms of the cathode

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5
Q

J.J Thompson’s Second Experiment

A

MEASURED CHARGE/MASS OF ELECTRON (E/M)
• Placed a large electromagnet outside the glass tube
• Adjusted the strength of the magnetic field
• Brought a beam of electrons down to its original position

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6
Q

Robert Millikan

A

MEASURED CHARGE OF ELECTRON
• Oil Drop Experiment
• X- rays to ionise air between plates
• Negatively charged oil droplets between two charged plates
• Adjusted charge on plates until an oil droplet was stationary

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7
Q

Thompson’s Plum Pudding Model

A

An atom is a sphere of positive charge

Electrons are embedded in the sphere at random

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8
Q

Ernest Rutherford

A

DISCOVERED NUCLEUS (+)
• Bombarded gold foil with alpha particles (+)
• Some went through. Some were deflected.
• Phosphorescent screen made of zinc sulfide to detect alpha particles
• Most of the atom is empty space

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9
Q

Discovery of Proton (+)

A
  • Bombarded other things
  • Alpha particles broke nuclei of light atoms to release protons
  • In heavier atoms, large positive nuclear charge repelled alpha particles
  • Atoms consist of a small dense positive core (nucleus)
  • Protons were located in nucleus
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10
Q

James Chadwick

A

DISCOVERED NEUTRON
• Bombarded beryllium with alpha particles
• They knicker neutrons our of nuclei of beryllium atoms
• Paraffin wax to detect them
• Neutrons knocked protons out of paraffin wax
• Radiation with particles with no charge came from beryllium (neutron)

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11
Q

Power of Neutrons

A

They brought about the splitting of atoms of uranium to release nuclear energy

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12
Q

Who proposed a theory of atoms in 1808

A

John Dalton

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