1. The document discusses concepts related to electron configurations including ground states, excited states, and impossible states. 2. It notes that Hund's rule and the Aufbau principle can be violated but not Pauli's exclusion principle. 3. Periodic trends are discussed such as how atomic radius decreases down a group but increases across a period due to effective nuclear charge. Ionic radius is also smaller for cations and larger for anions compared to neutral atoms. 4. Ionization energy increases across a period but decreases down a group due to size and electrostatic effects. Electron affinity is the energy released when an electron is added to form a negative ion.