The Smallest Matter Worksheet
Name:		Date:
During the early 20th century, New Zealand scientist Ernest Rutherford conducted an experiment. He
shot electrically charged alpha particles at thin gold foil. This experiment helped Rutherford and Danish
scientist Niels Bohr develop a way of thinking about the structure of an atom.
Follow the directions to simulate Rutherford's Gold Foil Experiment.
Equipment:
•	Solid object to represent the detecting screen.
•	Small solid objects to represent the protons in the nucleus of gold atoms.
•	Round object to represent alpha particles (positively charged particles made up of two neutrons
and two protons).
Directions:
Select a flat surface. Set up the detecting screen in a U or circular shape, leaving an opening for the
alpha particle. Place the small objects that represent the protons of a gold atom in the center of the area
within the detecting screen. The space between the protons represents neutrons.
Alpha particle o
0
0
0
Detecting screen, protons within the
nucleus of gold atoms, and space
between protons to represent
neutrons of gold atoms
Detecting screen, protons within the nucleus of gold atoms, and space between protons to represent
neutrons of gold atoms
1. Observe the experiment setup and hypothesize what will happen when you roll alpha particles
at the gold foil and why.
Roll the round object representing alpha particles toward the gold foil. Observe and record your
observations for each roll.
Roll 1:
Roll 2:
Roll 3:
Roll 4:
Roll 5:
Roll 6:
Roll 7:
Roll 8:
Roll 9:
Roll 10:
vvEPA
United States	RadTown Radioactive Atom Activity Set	EPA 402-B-19-031
Environmental Protection	'
Agency	https://www.EPA.gov/RadTown/Activity-l-Atomic Discoveries

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3. Share your conclusions.
What conclusions did you form about the structure of an atom based on the experiment and
your observations?
From the gold foil experiment, Rutherford and Bohr concluded that each atom was mostly
empty space, but also contained a central mass that the alpha particles could not pass through.
Rutherford concluded that the central mass must have a positive charge. Why did he think that?
The Rutherford-Bohr Theory of Atomic Structure
Electrons
Nucleus
rnA United States _	RadTown Radioactive Atom Activity Set	EPA 402-B-19-031
Environmental Protection	7
* mAgency	https://www.EPA.gov/RadTown/Activity-l-Atomic Discoveries

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