Modern Atomic Theory Electrons in the Atom Electromagnetic Spectrum

1. Modern Atomic TheoryElectrons in the AtomElectromagnetic Spectrum

2. Fundamentals of Light

3. Neon advertising signs are formed from glass tubes bent in various shapes. • An electric current passing through the gas in glass tube makes the gas glow with its own characteristic color. • Why does each gas glow with a specific color of light?

4. LIGHT The ground state is the lowest energy level that an electron can occupy.

5. The excited state is a higher energy level that an electron may move to after absorbing energy.

6. The amount of energyabsorbed by the electron is equal to the energy of the photon which is emitted.

7. A quantum leapis the jump in energy level that an electron will make after absorbingthe correct quanta of energy. A quantum is a packet of energy that electrons absorb to change energy levels.

8. Light (photons): form of some of the electromagnetic radiation (energy) released by electrons as theyreturnto their ground state from their excited state.

9. Energy absorbed (released) see light • Energy  increases • Ground state  excited state (where electrons are suppose to be) Sun gives tremendous amount of energy (ground  excited)

10. ELECTROMAGNETIC RADIATION • All electrons are sitting in ground state • Turn on light  electricity (goes to a higher e- level) • If electricity still on  out • Little burst of energy Lights off  Ground state Lights on  excited state (always little bursts of energy going on)

11. Excited Gases & Atomic Structure

12. Electromagnetic radiation.

13. Electromagnetic radiationis a form of energy that exhibitswavelikebehavior as it travels through space.

14. Electromagnetic Radiation • Most subatomic particles behave as PARTICLES and obey the physics of waves.

15. Waves • Wavelength () –(Greek letter lambda), length of one complete wave (distance between crests) • Frequency () – (Greek letter nu) # of waves that pass a point during a certain time period • hertz (Hz) = 1/s • Amplitude (A) – distance from the origin to the trough or crest

16.  crest A A origin trough  Waves greater amplitude (intensity) greater frequency (color)

17. wavelength Visible light Amplitude wavelength Node Ultaviolet radiation Electromagnetic Radiation

18. Light • The wavelength and frequency of light are inversely proportional to each other. Low energy High Energy

19. The Electromagnetic Spectrum

20. Light • Sunlight consists of light with a continuous range of wavelengths& frequencies. • The electromagnetic spectrum consists of radiation over a broad band of wavelengths.

21. ElectromagneticSpectrum In increasing energy, ROYGBIV

22. increasing frequency increasing wavelength Electromagnetic Spectrum Long wavelength --> small frequency (low energy) Short wavelength --> high frequency (High energy)

23. Types of EM Radiation • Radiowaves • lowest energy EM radiation • Receives in radio ( unscrables)

24. Types of EM Radiation • Radar • Military, space, sonar, weather • Speeding (cops) • Microwaves • penetrate food and vibrate water & fat molecules to produce thermal energy • Telephone & cell phone signals

25. Types of EM Radiation • Infrared Radiation (IR) Used by military ( to see in drk) • slightly lower energy than visible light • can raise the thermal energy of objects • thermogram - image made by detecting IR radiation

26. Infrared Measures Heat Every object with a temperature above absolute zero radiates in the infrared.

27. Infrared in Society • Oceanography • Firefighting • Commercial Applications

28. R O Y G. B I V red orange yellow green blue indigo violet Types of EM Radiation • Visible Light • small part of the spectrum we can see • ROY G. BIV - colors in order of increasing energy

29. How to split Light: a) Prism (curve each wave length)

30. B) Mirror & Water  wavelength of light

31. A spectroscope: device used to view the visible wavelengths of light produced by different atoms. The wavelengths are visible as bright lineson the spectrum.

32. Spectrum of White Light ROY G BIV

33. Types of EM Radiation • Ultraviolet Radiation (UV) • slightly higher energy than visible light • Types: • UVA - tanning, wrinkles • UVB - sunburn, cancer • UVC - most harmful, sterilization Bumble bee Insects can see uv waves

34. Types of EM Radiation • Ultraviolet Radiation (UV) • Ozone layer depletion = UV exposure!

35. Types of EM Radiation • X rays • higher energy than UV • can penetrate soft tissue, but not bones • Put a lead vest over body

36. Radiation treatment using radioactive cobalt-60. Types of EM Radiation • Gamma rays • highest energy EM radiation • emitted by radioactive atoms • used to kill cancerous cells

37. The particular wavelength of light produced is specific for each element and can be used to identify it.

38. Line Emission Spectra of Excited Atoms • Excited atoms emit light of only certain wavelengths • The wavelengths of emitted light depend on the element.

39. Spectrum of Excited Hydrogen Gas

40. Line Spectra of Other Elements

41. Slit that allows light inside Light Spectrum Line up the slit so that it is parallel with the spectrum tube (light bulb) Scale

42. A flame test : method used to identify and element by the color of flame it produces. Ex: copper produces a characteristic green flame.

43. Fingerprints of Light Example conclusion • During this experiment, several different metal ions emit a distinct color when held into a flame . Because each metal emitted a different color, the metal cation can be identified. In this experiment, Barium, copper, strontium, potassium, lithium, and sodium, were identified. Colors were yellow-green, green, red, violet, red-orange, & orange. • Important concepts involved in this lab include atomic orbitals, the energy states of atoms, ions, and atomic emission. Electrons orbit the nucleus in “shells”, each shell has a principle quantum number. Each electron has a ground stage but when it acquires energy it becomes “excited” and gains a higher principle quantum number. The emission spectra, or how it is seen with light, is obtained by adding energy and then having the electrons fall to the ground ( excited state) • Thus, identification of elements can be done because of the different colors that are given off by the jumping electrons. • SOURCES OF ERRORS: different flame/gas levels, contaminated solutions, different ions held in flame different lengths of time, color blindness

44. The Electric Pickle • Excited atoms can emit light. • Here the solution in a pickle is excited electrically. • The Na+ ions in the pickle juice give off light characteristic of that element.

45. Light • Light • How are the wavelength and frequencyof light related?

46. Electromagnetic Radiation • Waves have a frequency • Use the Greek letter “nu”, , for frequency, and units are “cycles per sec” • All radiation:  •  = c • where c = velocity of light = 3.00 x 108m/sec

47. EM Spectrum • Frequency & wavelength are inversely proportional c =  c: speed of light (3.00  108 m/s) : wavelength (m, nm, etc.) : frequency (Hz)

48. WORK:  = c   = 3.00  108 m/s 4.34  10-7 m EM Spectrum • EX: Find the frequency of a photon with a wavelength of 434 nm. GIVEN:  = ?  = 434 nm = 4.34  10-7 m c = 3.00  108 m/s = 6.91  1014 Hz

49. Light • According to the wave model, light consists of electromagnetic waves. • Electromagnetic radiationincludes radio waves, microwaves, infrared waves, visible light, ultraviolet waves, X-rays, and gamma rays. • All electromagnetic waves travel in a vacuum at a speed of 2.998  108 m/s.

50. Quantum Theory • The energy of a photon (light quanta) is proportional to its frequency. (E = h x v) E: energy (J, joules) h: Planck’s constant (6.6262  10-34 J·s) : frequency (Hz) E = h