1. Chapter 5 Electronic Structure

2. Light Through a Prism W White light (sunlight) is a blend of all colors (ROY G BIV) combined together. T The wavelength (λ) and frequency (υ) for each color are unique to that color. A As light passes through a prism… - the different wavelengths of the colors are separated. - individual colors can be detected by the eye. - a rainbow appears.

3. The Electromagnetic Spectrum ll substances (radioactive or not) emit electromagnetic radiation. light: O Only part of the spectrum that human eyes can detect is visible (ROY G BIV) A All other radiations have wavelengths that are either too long or too short for our eyes to detect. The Electromagnetic Spectrum (EM spectrum) is made of the different forms of electromagnetic waves and is based on the frequency and wavelength of the wave. EM waves do not require a medium to travel…..

4. Cosmic rays Microwaves Increasing danger too long to see too short to see 7.4 x 10-6 m longest 4.2 x 10-6 m shortest

5. The following list [A to G] names the forms of the EM spectrum in order of energy, frequency and wavelength. [A…..largest wavelength, lowest frequency & lowest energy] A. radio waves (includes AM, FM, TV, radar, shortwaves) used for communication B. microwaves -- used in cooking; can penetrate air, glass, paper and plasticThe following list [A to G] names the forms of the EM spectrum in order of energy, frequency and wavelength. [A…..largest wavelength, lowest frequency & lowest energy] A. radio waves (includes AM, FM, TV, radar, shortwaves) used for communication B. microwaves -- used in cooking; can penetrate air, glass, paper and plastic

6. C. infrared (heating lamps) felt as warmth; used to keep food warm D. visible (only portion that humans can see; smallest part of the spectrum) ROY G. BIV…violet has the greatest energy, frequency, and smallest wavelength of all the colors E. ultraviolet (causes sunburn)

7. F.x-rays (medical use) will pass through the human body with the exception of some bones and tissues G. gamma rays (treatment of cancer ) can kill living cells [G…..smallest wavelength, highest frequency & highest energy]

8. Wavelength vs. Frequency W Wavelength (λ): distance b/n crests of a wave. Wavelength crest trough Wavelength long wavelength short wavelength

9. *** higher frequency = higher energy *** F Frequency (ν): # of wavelengths that pass a certain point in a given amount of time. - units are Hertz (Hz) T These 2 waves are traveling at = speeds… which wave will have more crests cross the ‘finish line’ in a matter of one min.? FINISH low frequency high frequency = short wavelength = long wavelength

10. Wave Calculations w wavelength (λ) and frequency (υ) are inversely related. a all waves on the EM spectrum travel at the speed of light (c). c = λ(ν) c c = speed of light = 3.00 x 108 m/s. t to solve for λ … ν ν c λ = ν o solve for υ … c ν = λ λ λ

11. P Practice… Calculate the υ of a wave that has a wavelength of 5.00 x 10-6 m. c ν = λ ν = 3.00 x 10 8 5.00 x 10 -6 ν 6.00 x 10 13 Hz = What is the λ of radiation with a frequency of 1.50 x 1013 Hz? c λ = ν λ = 3.00 x 10 8 1.50 x 10 13 λ = 2.00 x 10 -5 m Does this radiation have a shorter or longer λ than red light? longer…red light ~ 7.4 x 10-6 m

12. M Max Planck explained that light is emitted in packets (quanta) called ‘photons’ which are distinct bundles of energy. P Planck also assumed that energy of a photon is directly proportional to the frequency of the light. E = h(ν) E E = energy (in Joules) υ υ = frequency h h = Planck’s constant (6.626 x 10-34 J/Hz) P Practice… C Calculate the energy of radiation with a υ of 5.00 x 1015 Hz. E = h(ν) E = 6.626 x 10-34 (5.00 x 1015) E = 3.31 x 10 -18 J 3.31 x 10 -18 J ν h h = E h

13. Obj. 5…Atomic Spectra a all elements will emit light when excited (i.e. by electricity). toms absorb energy and then emit an = amount of energy in the form of light. - atoms emit a characteristic color - Ne = orange - red - Na = bright yellow i if we pass this light through a prism (separate the λ) we get an atomic emission spectrum. ex. of wavelengths emitted set-up

14. Obj. 5 cont… e emission spectra are unique to particular elements. o only show certain lines of the continuous spectrum (white light). h have helped us gather a lot of info. about our universe! a atomic absorption spectra shows colors missing from the continuous spectrum (missing λ were absorbed by the element). continuous absorption emission

15. Obj. 6-7…How Atoms Absorb and Emit Energy e e- are found on certain energy levels (orbitals) around the atom. - there is a maximum of seven energy levels in an atom. - an e- requires one ‘quanta’ of energy to jump to the next energy level. - e- on the energy level closest to the nucleus have the lowest energy. The 7th energy level has the highest energy. - at their lowest energy level are considered to be at the ground state (most stable). i if e- absorb a quantum or more of energy (from electricity), they can jump to higher energy levels (excited state). e e- must lose energy in order to fall from the excited state back to the ground state. - this energy is emitted in the form of visible light!

16. Obj. 6-7 cont… ‘Heinsburg’s uncertainty principle’ states that it is impossible to know exactly where an e- is, b/c it is constantly in motion.