Chapter 2 - Atoms

Question 1

Who said matter was made up of small particles

Answer 1

Greek philosophers

Democritus was one

Question 2

How was the Electron discovered

Answer 2

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

Question 3

Crookes Paddle Wheel

Answer 3

Investigate property of cathode rays

Vanes always turned away from cathode

Question 4

J.J Thompson

Answer 4

• 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

Question 5

J.J Thompson’s Second Experiment

Answer 5

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

Question 6

Robert Millikan

Answer 6

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

Question 7

Thompson’s Plum Pudding Model

Answer 7

An atom is a sphere of positive charge

Electrons are embedded in the sphere at random

Question 8

Ernest Rutherford

Answer 8

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

Question 9

Discovery of Proton (+)

Answer 9

• 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

Question 10

James Chadwick

Answer 10

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)

Question 11

Power of Neutrons

Answer 11

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

Question 12

Who proposed a theory of atoms in 1808

Answer 12

John Dalton