chem ch.2

Energy, Light, and Quantization/ Electron Energy Levels and Transitions (Bohr Model) / The Quantum Model: Orbitals and Probability / Electron Configuration and Orbital Filling / Electron Structure and the Periodic Table / Periodic Trends and Atomic Properties

Quantum theory- Electromagnetic wave

radiation energy propagated by electric and magnetic fields that oscillate in intensity as they travel

• ex) visible light, x-rays, radiowaves, microwaves

Properties of a wave

1. frequency (ν): number of cycles per sec (Hz)

2. wavelength (λ): distance btw equivalent points

3. Amplitude (A): height of the crest- intensity

relationship btw wavelength and frequency

c = λν
λ= c/ν

Quantinization of Energy: Blackbody radiation - Max Planck

• concept: a solid heated to very high (~1000k) emits visible light

• problem classical physics says matter can absorb or emit any quantity of energy. fails to explain the wavelength/intensity relationship of blackbody radiation

• Solution: Max Planck- energy is “quanitized” in whole-number multiples hν (ΔE = nhν)
  - ΔE= difference in energy
  - n= whole number (integer)

Photoelectric Effect- Albert Einstein

• concept: light striking a metal surface ejects electrons

• problem: the light must have a minimum “threshold frequency.” Below this frequency, no electrons are ejected, regardless of intensity

• solution: light consists of “particles” called photons (Ephoton= hv= hc/λ)

de Broglie Wavelength

• equation (Einstein): E=mc² (don’t need to know)

• Summary) Wave-Particle Duality:
  - matter and energy both have dual particulate and wave properties
  electrons exhibit wavelength behavior
  - diffraction: scattering of light by a regular array of points or lines
  - electrons moving through space at fast rates are diffracted by crystals

• UNDERSTAND: photons/waves behave like particles, and electrons thought of particles exhibit wave-length behavior. When we see how electrons behave in atoms, we think of them as waves moving around space.