HS-PS1-8: Modeling Fission, Fusion and Radioactive Decay
Also called NGSS HS-PS1-8 · Topic: Structure and Properties of Matter · Physical Science
The Official Wording
Develop models to illustrate the changes in the composition of the nucleus of the atom and the energy released during the processes of fission, fusion, and radioactive decay.
Clarification statement: Emphasis is on simple qualitative models, such as pictures or diagrams, and on the scale of energy released in nuclear processes relative to other kinds of transformations.
Assessment boundary: Assessment does not include quantitative calculation of energy released. Assessment is limited to alpha, beta, and gamma radioactive decays.
NGSS Lead States, 2013 · Read it on nextgenscience.org · checked October 15, 2026
What HS-PS1-8 Means in Plain English
High school students draw or build simple models of the nucleus to show what happens to its protons and neutrons when a heavy nucleus splits, light nuclei join, or an unstable nucleus decays. They compare how much energy these changes release with ordinary chemical reactions.
Models stay qualitative: no calculating energy from mass, and only alpha, beta and gamma decay. The idea links to how the Sun shines (HS-ESS1-1) and how rock ages are measured (HS-ESS1-5).
HS-PS1-8 I Can Statements
- I can show how a nucleus changes in alpha and beta decay.
- I can tell fission from fusion using a simple model.
- I can explain why nuclear changes release far more energy than burning.
HS-PS1-8 Worked Example
A tabletop model using two colors of pop beads, one for protons and one for neutrons.
What happens to the protons and neutrons in a nucleus during decay and fusion?
Set It Up: Red pop beads for protons, green pop beads for neutrons, and a periodic table to name each nucleus.
- Build carbon-14 with 6 red and 8 green beads, then swap one green bead for a red one.Beta decay: 7 protons, 7 neutrons = nitrogen-14
- Polonium-210 is too big to build, so write 84 p and 126 n on a card and subtract a 2-red, 2-green cluster.Alpha decay: 82 p and 124 n, now lead-206
- Join a deuterium cluster (1 red, 1 green) with a tritium cluster (1 red, 2 green).Fusion: helium-4 plus one spare neutron
- Note that gamma decay changes no beads, only releases energy.Same atom type, less energy
- Compare energy per atom: nuclear changes against a lit match.Nuclear: millions of times more
Alpha and beta decay change the number of protons, so the atom becomes a different kind, while gamma decay only gives off energy.
Why it works: The strong force holds nuclei together much more tightly than electrons are held in molecules, so rearranging a nucleus releases vastly more energy.
Common Mistakes with HS-PS1-8
Mixing up nuclear and chemical change
“In decay, the atom gains electrons and becomes a new element.”
Try this: The element changes only when the number of protons in the nucleus changes. Electrons alone never turn carbon into nitrogen.
Swapping fission and fusion
Saying the Sun splits hydrogen atoms apart
Try this: Fission splits a heavy nucleus like uranium. Fusion joins light nuclei like hydrogen isotopes into helium, which is what powers the Sun.
Thinking a beta particle comes from the electron cloud
Drawing an outer electron flying off during beta decay
Try this: In beta decay a neutron inside the nucleus turns into a proton and shoots out a new electron, so the nucleus gains a proton.
Where HS-PS1-8 Fits
Practice HS-PS1-8
Quick Check
- Uranium-238 gives off an alpha particle. What element does it become?
- Does gamma decay change the element?
- Why can a small amount of nuclear fuel run a power plant for months?