1What was the purpose of Milikan’s oil drop experiments?
To determine the charge of an electron.
2Give one way of detecting the presence of cathode rays in a vacuum tube?
Using a Maltese cross you’ll see a fluoresce be produced with a shadow produced.
3Give another way of detecting the presence of cathode rays in a vacuum tube?
Using a paddle wheel, the wheel will move towards the positive electrode.
4Name the scientist who identified cathode rays as subatomic particles and also measured the charge to mass ratio?
J.J. Thompson
5What is the proper name for cathode rays?
Electrons (rays)
6Define mass number.
The number of protons and neutrons in the nucleus of an atom.
7Define relative atomic mass.
The average mass of the isotopes of an element taking their abundances into account relative to 1/12 of the mass of the carbon-12 atom.
8Describe Rutherford’s ‘gold foil’ experiment.
Rutherford bombarded thin gold foil with alpha particles and used a screen to detect the particles.
9What were the observations of Rutherford’s experiment?
Most alpha particles went straight through - atom is mostly empty space.
10What does it mean when some alpha particles reflected at large angles?
The nucleus is small.
11What does it mean when a tiny amount of alpha particles deflected back the original path?
The nucleus is small and dense.
12Describe Thomson’s ‘plum pudding’ model.
The atom is a positively charged sphere with negatively charged electrons embedded in it.
13What is an element according to Robert Boyle?
Cannot be broken into anything simpler.
14What are alpha particles?
Helium nucleus with two protons and two neutrons.
15Give two properties of cathode rays.
Travel in straight lines.
16Give another property of cathode rays.
Negligible mass.
17Give one more property of cathode rays.
Negatively charged.
18State two assumptions of Dalton’s Atomic Theory of 1808.
Atoms are small and indivisible.
19Name the scientist who measured the ratio of charge to mass of an electron (e/m).
J.J. Thompson
20Name the scientist who proved that electrons in an atom reside in an electron cloud surrounding a small dense positive nucleus.
Rutherford
21Name the scientist who measured the charge on the electron.
Millikan