Indiana Science HS-PSII-10.4

ScienceGrades 9–12Physical Science

The Standard

Apply the conservation of mass, conservation of charge, and conservation of linear momentum principles to describe the results of a radioactive particle undergoing either alpha or beta decay.

Indiana Academic Standards for Science (2023) · Modern Physics

Teacher's field guide

What This Standard Means

What Students Need to Do: Students balance mass number and charge in alpha and beta decay equations. They show how emitted particles and the daughter nucleus share momentum, including the antineutrino in beta-minus decay.
What Mastery Looks Like: A student can complete an alpha or beta-minus decay equation with the correct particles, mass numbers, and charges. They can draw recoil arrows and explain why beta-minus decay needs an antineutrino to account for momentum.
Common Misconceptions: Students may subtract one from the mass number in beta-minus decay or think the emitted electron comes from an atom's electron cloud. They may leave out the antineutrino or assume the daughter nucleus stays still. They may also confuse mass number with measured mass, which can change as energy is released.
How to Assess It: Exit ticket: Complete ¹⁴₆C → ___ + ___ + ___ for beta-minus decay. Check the mass numbers and charges, then explain why the daughter nucleus can recoil.

Lesson moves

Ways to Teach It

Give students cards marked ²⁴¹₉₅Am, ⁴₂He, and ²³⁷₉₃Np; have them balance the decay and place recoil arrows.
Ask students to write why an electron and a daughter nucleus alone may not account for momentum in beta-minus decay.
Run a decay relay: teams fill missing products in uranium-238 alpha decay and carbon-14 beta-minus decay, then check charges.
Show a smoke detector diagram labeled americium-241; ask students to identify the alpha particle and predict the daughter's recoil direction.

Free download