BIG topics... Light (electromagnetic radiation) particle/wave dual nature of light c, λ, ט & E Quantum theory (wave mechanical model) Bohr model of Hydrogen atom absorption/emission orbital shapes Electron configurations orbital, e- configuration noble gas notation Aufbau, Pauli & Hund (names not tested!)

Waves Wavelength () - length of one complete wave. Common units: m or nm Frequency () - # of waves that pass a point during a certain time period Common Units: hertz (Hz) = 1/s = s-1 Amplitude (A) - distance from the origin to the trough or crest Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Wavelength and Frequency “nu” “lamda” c = speed of light (3.0 x 108 m/s)‏ = frequency (s-1)‏ = wavelength (m)‏ c =  Highest energy Moderate energy Lowest energy E = energy (Joules or J)‏ h= Planck’s constant (6.626 x10-34 J s)‏ = frequency (s-1)‏ E = h 

Visible part of EM SPectrum 400 nm – 700 nm Waves 1/33,000” long Waves 1/70,000” long Red Orange Yellow Green Blue Indigo Violet PRISM Slit Ray of White Light All light is bent passing through a prism; violet is bent most and red least. A beam of sunlight produces a continuous band of rainbow colors showing that light is a mixture of colors.

Electromagnetic Spectrum “The Electromagnetic Spectrum”   Description: This slide depicts the electromagnetic spectrum from gamma rays through radio waves. Basic Concepts          All forms of electromagnetic radiation are not identical          All forms of electromagnetic radiation travel at the same speed in a vacuum (the speed of light, c = 3.00 x 108 m/sec).          Wavelength and frequency are inversely proportional for a wave traveling at a constant speed.          Energy and frequency are directly proportional for electromagnetic waves traveling at the speed of light. Teaching Suggestions Use this transparency to review the relationship of visible light to other types of radiation. Explain that all of the rays and waves shown are types of electromagnetic radiation. Point out that they differ essentially from each other only in energy level, wavelength, and frequency. Try the analogy of an ocean wave to help students understand electromagnetic waves. Question 6 can be used to assess the students understanding of wave velocity, wavelength, and frequency. Questions: List the ways in which visible light is different from the other types of radiation shown in the diagram. List the ways in which all of the types of radiation shown in the diagram are similar. You are told that sound waves cannot travel in a vacuum. Are sound waves a types of electromagnetic radiation? Explain your logic. Radio waves can go around an obstruction if the obstruction is smaller than the radio wave’s wavelength. What would you expect to happen if visible light were beamed at a thin wire 2 x 10-5 centimeter thick? Explain your answer. For electromagnetic waves traveling at the speed of light, the wavelength is inversely proportional to frequency, as expressed by the equation c = fl, where c = speed of light in vacuum (3.00 x 108 meters/second), f = frequency, and l= wavelength. Using this equation, calculate the frequency of a 3-meter radio wave traveling at the speed of light. Compare your answer with the diagram. Suppose that at a particular beach the ocean waves are traveling at a speed of 2 meters/second. If you know that the distance between waves is 10 meters, can you calculate how often they hit the shore? Explain your answer. For electromagnetic waves traveling at the speed of light, the energy of a single photon is expressed by the equation E = hf, where E = energy, f = frequency, and h = Planck’s constant, 6.6 x 10-33 joules/hertz. Which has more energy, a photon of visible light or a photon of radar, if both traveling at the speed of light? Do you think you can calculate the energy of an ocean wave using this energy equation? Explain your answer. Electromagnetic Spectrum

Excitation of Hydrogen Atoms

Return to Ground State

An Excited Lithium Atom Excited Li atom Energy Photon of red light emitted Li atom in lower energy state

Quantum Theory Max Planck (1900)‏ Observed - emission of light from hot objects Concluded - energy is emitted in small, specific amounts (quanta)‏ Quantum - minimum amount of energy gained or lost by an atom Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Continuous vs. Quantized Energy B quantized Energy A continuous A B continuous quantized

Further away from nucleus means higher energy level… Bohr Model of Hydrogen Great theory, BUT it turned out to be totally wrong!! Next week we’ll see a better theory  e Nucleus Possible electron orbits

Emission Spectrum of Hydrogen 1 nm = 1 x 10-9 m = “a billionth of a meter” 410 nm 434 nm 486 nm 656 nm

Continuous and Line Spectra Visible spectrum l (nm) light 400 450 500 550 600 650 700 750 nm Na H Ca Hg

Preview....Orbital Shapes