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electromagnetic radiation

electromagnetic radiation. a form of energy that exhibits wave-like behavior as it travels through space. Visible light. Type of electromagnetic wave The only type of electromagnetic wave that we can see = visible light. The atom and visible light.

debra-mcintosh
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electromagnetic radiation

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  1. electromagnetic radiation • a form of energy that exhibits wave-like behavior as it travels through space.

  2. Visible light • Type of electromagnetic wave • The only type of electromagnetic wave that we can see = visible light

  3. The atom and visible light • In the early 1900s, scientists observed certain elements emitted visible light when heated in a flame. • Analysis of the emitted light revealed that an element’s chemical behavior is related to the arrangement of the electrons in its atoms.

  4. Light Moves in Waves • Visible light is a type of electromagnetic radiation, a form of energy that exhibits wave-like behavior as it travels through space. • All waves can be described by several characteristics.

  5. Characteristics • The wavelength (λ) is the shortest distance between equivalent points on a continuous wave. • The frequency (ν) is the number of waves that pass a given point per second. • The amplitude is the wave’s height from the origin to a crest.

  6. The speed of light (3.00 X 108 m/s) is the product of it’s wavelength and frequency c = λν.

  7. What is the frequency of light that has a wavelength of 550 nm? (1m = 1 x 109 nm)?

  8. What is the wavelength of light, in cm, that has a frequency of 9.60 x 1014 Hz (1/s)?

  9. What is the frequency of light (Hz) that has a wavelength of 740 nm (1m = 1 X 109 nm)?

  10. The wave model of light cannot explain all of light’s characteristics. • Matter can gain or lose energy only in small, specific amounts called quanta. • A quantum is the minimum amount of energy that can be gained or lost by an atom.

  11. Albert Einstein proposed in 1905 that light has a dual nature. • A beam of light has wavelike and particlelike properties. • A photon is a particle of electromagnetic radiation with no mass that carries a quantum of energy.

  12. Sunlight splits into a spectrum of colors when it passes through a prism. • Colors of the spectrum include red, orange, yellow, green, blue, indigo and violet. • Red light has the longest wavelength and the lowest frequency, while violet light has the shortest wavelength and the highest frequency.

  13. Dispersion of white light by a prism

  14. Every element emits light after it absorbs energy. The light that is emitted (atomic emission spectra) is different for every element, and differs from white light because it is not continuous.

  15. The atomic emission spectrum of an element is the set of frequencies of the electromagnetic waves emitted by the atoms of the element.

  16. Each element’s atomic emission spectrum is unique.

  17. Planck showed that the amount of radiant energy (E) absorbed or emitted by a substance is proportional to the frequency of the radiation.

  18. Dispersion of white light by a prism

  19. A photon of red light carries less energy than a photon of blue light

  20. Ephoton = hEphoton represents energy. h is Planck's constant. represents frequency Planck’s constant has a value of 6.626 X10–34 J ● s.

  21. What is the energy of a photon with a frequency of 2.94 x 1015 cycles per second (s-1 or Hz)?

  22. What is the energy of a light particle with a wavelength of 675 nm?

  23. Bohr’s model

  24. The Quantum Mechanical Model of an atom • Louis de Broglie (1892–1987) hypothesized that particles, including electrons, could also have wavelike behaviors.

  25. Heisenberg showed it is impossible to take any measurement of an object without disturbing it. • The Heisenberg uncertainty principle states that it is fundamentally impossible to know precisely both the velocity and position of a particle at the same time. • The only quantity that can be known is the probability for an electron to occupy a certain region around the nucleus.

  26. What does this all mean? • Electrons do not move in circular paths around the nucleus of an atom • It is impossible to determine the exact location of an electron at any given time • We can only calculate the probability that an electron will occupy a region around the nucleus

  27. Energy Levels • Electrons can exist in energy levels 1-7 • The higher the energy level, the further from nucleus • Energy level 1 is closer to the nucleus of an atom than energy level 2

  28. Energy levels • The maximum number of electrons that can occupy an energy level is given by the formula 2n2, where n is the # of the energy level. • 1st energy level up to 2 electrons • 2nd energy level up to 8 electrons • 3rd energy level up to 18 electrons • 4th energy level up to 32 electrons

  29. Energy levels can be divided into sublevels • Each energy level can be divided into sub levels (s, p, d, f) • Each sublevel contains orbitals • Each orbital can contain a maximum of 2 electrons

  30. Energy sublevel • Max of 2 electrons per orbital • “s” sublevel – 1 orbital per sublevel (up to 2 total electrons) • “p” sublevel – 3 orbitals per sublevel (up to 6 total electrons • “d” sublevel – 5 orbitals per sublevel (up to 10 total electrons) • “f” sublevel – 7 orbitals per sublevel (up to 14 total electrons)

  31. Sum it up • Electrons surround the nucleus in electron clouds • Electrons can exist in different energy levels (1-7) • Each energy level contains sublevels. Possible sublevels for each energy level (s,p,d,f) • Each sublevel has orbitals. • S= 1 orbital p= 3 orbitals d= 5 orbitals • f= 7 orbitals

  32. Electron configuration – the way in which electrons are arranged in energy levels outside of the nucleus. • Orbital notation – a way of showing the electron configuration using arrows to represent each electrons and boxes to represent each orbital.

  33. Aufbau principle – electrons enter orbitals of lowest energy first. 2. Pauli exclusion principle – an atomic orbital may hold at most two electrons. Electrons within the same orbital have opposite spins. 3. Hund’s rule – one electron must be put in each orbital of a sublevel before any one orbital can have two electrons in it.

  34. Electron Configurations • You may be saying, seriously I have to memorize all of that! YUK! • Don’t give up, it’s not that hard! • I promise I have good news! • Great news!! If you can read, you can predict the location of the electrons in an atom without memorizing anything except the letters s, p, d, f • Can you read and memorize s,p,d,f?

  35. Electron Configurations • Oh, wait…. I forgot you have to be able to master one more skill. This one may be tough. • Can you count to 7?

  36. GREAT! • THE ONLY PRERESIQUITE FOR WRITING ELECTRON CONFIGURATION IS THE ABILITY TO READ, COUNT TO 7, AND MEMORIZE s, p, d, f!!! • FINALLY, SOMETHING EASY!!!!! SOMETHING YOU HAVE BEEN DOING SINCE YOU HAVE BEEN 5!

  37. 4d 5s 4p 3d 4s s 1 2 p 1 3p 1 2 3 4 5 6 2 d 3 3s 1 2 3 4 5 6 7 8 9 10 4 5 2p 6 7 2s f 1 2 3 4 5 6 7 8 9 10 11 12 13 14 OK, so we’re going to use arrows pointing up or down to represent the electrons. Can you guess into which box the first electron would go given that it is attracted to the nucleus? 1s +

  38. 4d 5s 4p 3d 4s s 1 2 p 1 3p 1 2 3 4 5 6 2 d 3 3s 1 2 3 4 5 6 7 8 9 10 4 5 2p 6 7 2s H f 1 2 3 4 5 6 7 8 9 10 11 12 13 14 1s1 That’s right: it goes in the 1s sublevel. And its el. config is 1s2. Notice in the table above where H is – in the area designated as 1s. So where does the next electron go? 1s +

  39. 4d 5s 4p 3d 4s s 1 2 p 1 3p 1 2 3 4 5 6 2 d 3 3s 1 2 3 4 5 6 7 8 9 10 4 5 2p 6 7 2s He f 1 2 3 4 5 6 7 8 9 10 11 12 13 14 1s2 If you were thinking it went in the 2s, then you forgot that each orbital can hold up to two electrons. Note how He is right here in the area designated as 1s2 and so its el. config. is 1s2. 1s +

  40. 4d 5s 4p 3d 4s s 1 2 p 1 3p 1 2 3 4 5 6 2 d 3 3s 1 2 3 4 5 6 7 8 9 10 4 5 2p 6 7 2s Li f 1 2 3 4 5 6 7 8 9 10 11 12 13 14 1s2 2s1 Now that the 1s is filled, the next electron goes in the next sublevel – the 2s. Again note how Li is in 2s1. 1s Its full el. conf. is 1s2 2s1. What is Be’s el. conf? +

  41. 4d 5s 4p 3d 4s s 1 2 p 1 3p 1 2 3 4 5 6 2 d 3 3s 1 2 3 4 5 6 7 8 9 10 4 5 2p 6 7 2s Be f 1 2 3 4 5 6 7 8 9 10 11 12 13 14 1s2 2s2 Is this what you were thinking? Good. Now look at the periodic table above, what comes after the 2s sublevel? 1s The 2p sublevel. So what will the next el. conf. be? +

  42. 4d 5s 4p 3d 4s s 1 2 p 1 3p 1 2 3 4 5 6 2 d 3 3s 1 2 3 4 5 6 7 8 9 10 4 5 2p 6 7 2s B f 1 2 3 4 5 6 7 8 9 10 11 12 13 14 1s2 2s2 2p1 Is this what you were thinking? Notice how B is in the 2p1 spot. 1s So its full el. conf. is 1s2 2s2 2p1. What’s next? +

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