Student Exploration: Nuclear Decay
Vocabulary: alpha particle, atomic number, beta particle, daughter product, gamma ray, isotope, mass number, nuclear decay, positron, radioactive, subatomic particle
Prior Knowledge Questions (Do these BEFORE using the Gizmo.) The chart below gives the locations...
Prior Knowledge Questions (Do these BEFORE using the Gizmo .)
The chart below gives the locations, charges, and approximate masses of three subatomic
particles. The approximate mass of each particle is given in universal mass units (u).
Particle Location Charge Approximate mass
Proton Nucleus 1+ 1u
Neutron Nucleus 0 1u
–
Electron Orbitals 1 0u
1. The mass number of an atom is equal to the sum of protons and neutrons in the nucleus.
A helium atom has 2 protons and 2 neutrons. What is the mass number of this atom? _____
2. The atomic number of an element is equal to the number of protons in each atom of the
element. All helium atoms have 2 protons. What is the atomic number of helium? _____
Gizmo Warm-up
While most atoms are stable, some are radioactive, which
means that they have a tendency to undergo spontaneous
nuclear decay. The decay of radioactive atoms generally
results in the emission of particles and/or energy.
Several types of nuclear decay can be explored with the
Nuclear Decay Gizmo. On the Gizmo, check that Alpha
decay and Uranium are selected.
1. Click Play ( ), and then click Pause ( ) when the alpha particle is clearly visible. What is
an alpha particle made of? _____________________________________________
2. Click Play and observe. Besides the alpha particle, what else is emitted from the nucleus
during alpha decay? ________________________________________________________
Gamma rays are energetic electromagnetic waves; they are often emitted in nuclear decay.
2019
, Get the Gizmo ready:
Activity A:
Click Reset ( ).
Alpha decay Check that Alpha decay and Uranium are
selected.
Question: How does alpha decay change the nucleus of a radioactive atom?
1. Predict: As you observed in the warm-up activity, an alpha particle consists of two protons
and two neutrons. How will the emission of an alpha particle affect the following?
A. The atomic number of the atom: _________________________________________
B. The mass number of the atom: __________________________________________
2. Calculate: Turn on Write equation. What you see is an equation that shows the original
uranium atom on the left. The boxes on the right represent the daughter product—the atom
produced by radioactive decay—and the emitted alpha particle.
A. In the top left box, write the mass number of the daughter product and press “Enter”
on your keyboard. What is this number? ______________
B. In the bottom left box, write the atomic number of the daughter product and press
“Enter.” What is this number? ______________
C. In the next set of boxes, enter the mass number and atomic number of the alpha
particle, which has the same composition as the nucleus of a helium (He) atom. After
filling in the boxes in the Gizmo, write the completed equation below:
D. According to your equation, what isotope remains after the alpha decay of
uranium-238? (Note: You can look up element symbols on the periodic table.)
3. Check: Turn on Show equation, and click Play. The equation will appear at the end of the
animation. Was your prediction correct? _____________ If not, modify your equation above.
(Activity A continued on next page)
2019
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