Unit 2: Atomic Structure & Nuclear

A. Big Picture & Origins of Elements

• Sketch lifecycles of average and massive stars and element formation locations.

• Order major fusion steps (H → He → C… → Fe) and energy release.

• Explain iron (Fe) as the turning point for stellar fusion energy.

B. Nuclear Processes & Equations

• Identify fusion, fission, alpha (α), or beta (β-) from equation patterns.

• Balance nuclear equations by conserving mass number (A) and atomic number (Z).

C. Changes in α vs β Decay

• α decay: A decreases by 4, Z decreases by 2 (He emitted).

• β decay: Z increases by 1 (n → p + e−), A remains same.

D. Stability & Likely Decay

• Compute Z (protons) and N (neutrons = A - Z) from isotope symbol.

• Judge if isotope is stable or radioactive based on N:Z ratio; identify decay type.

E. Half-Life Reasoning

• Read decay graph/table for time to first half-life (50% remaining).

• Convert % remaining to number of half-lives and compute time using the equations:
  $(N = N<em>0(1/2)^{t/t</em>{1/2}})$ and
  (t = (# half-lives) × t_{1/2}).

F. Argument from Evidence (CER)

• Choose an isotope for a scenario using specific data points (decay type/energy + half-life) and justify the choice.