⚛️ Atomic Structure — Intermediate#

Scope — Electron configurations, shells/subshells, periodic trends, and simple atomic models.

Key concepts#

• Electron shells and subshells — n (shell), s/p/d/f (subshell).
• Aufbau principle, Pauli exclusion, Hund's rule — rules for filling orbitals.
• Periodic trends — atomic radius, ionization energy, electronegativity.

Seed Q&A triads#

• Q: What is the Aufbau principle?
  A: Electrons fill lowest-energy orbitals first (e.g., 1s → 2s → 2p).

• Q: How does ionization energy change across a period?
  A: Generally increases left → right due to stronger nuclear attraction on valence electrons.

• Q: Why do transition metals have variable oxidation states?
  A: Similar energies of ns and (n−1)d orbitals allow multiple electron removal patterns.

Short exercises#

• Write electron configurations for: C (6), Fe (26), Cu (29).
• Predict which has larger atomic radius: Na or Cl.