To Do

1. To Do • Quiz #4 next Wednesday (3/16). • 6th HW assignment due Wednesday, March 16, by 10 pm. • Exam 2: Thursday, March 17, 7:00 pm

2. Overall Goal: Properties • Nitrogen gas is inert, hydrogen gas is very reactive (with oxygen). • Water is a liquid, methane is a gas. • Oil and water don’t mix. To understand properties, we need to know molecular structure, which means we need to understand bonding, which means we need to understand atomic structure.

3. Big Ideas – Periodic Table • Originally arranged by atomic mass (protons not discovered). • See Ar & K; Co & Ni; Te & I. • Separated as “metals” and “nonmetals” (appearance/properties) • Chemical reactivity

4. Big Ideas – Periodic Table • The closer together the elements on the periodic table, the more chemically alike they are. • Especially true for elements in the same column. • “Missing” elements were predicted.

5. Big Ideas – Models • Models are not reality. • We use different models for different reasons. • A model should be as simple as possible, but not simpler (Einstein) • To answer more questions, the model must be more complex.

6. Various Atomic Models (Ch. 2) • Dalton: Indivisible atoms • J.J. Thomson: Atoms emit tiny negative particles. (Therefore atoms not indivisible!) • William Thomson (Lord Kelvin): formulates the Plum Pudding Model. • Rutherford: Some α-particles bounce back when shot at atoms. (There is a concentration of mass with a positive charge in the atom.) http://www.youtube.com/watch?v=5pZj0u_XMbc

8. Electromagnetic Spectrum

9. Different Wavelengths of Light

10. Questions • Which of the following has the longer wavelength? • Which of the following emits more energy? a) b)

11. Continuous Spectrum

12. Discrete Spectrum

13. Continuous vs. Discrete