Simulation Description: build Isotope, Atomic number and Mass number
Isotope Builder — Simulation
Students drag protons and neutrons into a nucleus. The element is identified live by proton count, and the isotope name (e.g. Carbon-14) updates instantly as neutrons are added. The same element with different neutron counts visually demonstrates what an isotope is.
Class Activity — “Same but Different”
Task: Build three isotopes of the same element and record what changes.
Step-by-step:
- Add 6 protons → Carbon-6 appears. Note: Z = 6, A = 6
- Add 6 neutrons → Carbon-12. This is the most common isotope
- Reset neutrons to 8 → Carbon-14. Same element, bigger mass number
- Reset. Try Hydrogen: 1 proton + 0 neutrons (Hydrogen-1), then add 1 neutron (Hydrogen-2, Deuterium), then 2 neutrons (Hydrogen-3, Tritium)
Discussion questions:
- “What stayed the same across all three carbon isotopes?” — Z, element name, chemical properties
- “What changed?” — N, A, mass, stability
- “Why is Carbon-14 useful in archaeology?” — leads into radioactive decay
Exit card: “Chlorine has two common isotopes: Cl-35 and Cl-37. Build both. How many neutrons does each have? Why is the average atomic mass on the periodic table 35.5?”