1. The Nature of Light: Its Wave Nature Light is a form of made of perpendicular waves, one for the electric field and one for the magnetic field All electromagnetic waves move through space at the same, constant speed

2. Characterizing Waves The amplitude is the

3. Characterizing Waves

4. The wavelength ( ) is

5. The frequency ( ) is the Characterizing Waves

6. LIGHT!!! wavelength and frequency are proportional wavelength frequency wavelength and energy are proportional wavelength energy energy and frequency are proportional energy frequency

7. Wavelength and Frequency Wavelength and frequency of electromagnetic waves are inversely proportional because the speed of light is constant, if we know wavelength we can find the frequency, and vice versa

8. Calculate the wavelength of red light (nm) with a frequency of 4.62 x 10 14 s −1 Calculate the wavelength (m) of a radio signal with a frequency of 106.5 MHz

9. Color The color of light is determined by a spectrum RedOrangeYellowGreenBlueViolet When an object absorbs some of the wavelengths of white light and reflects others, it appears colored

10. Types of Electromagnetic Radiation Electromagnetic waves are classified by their wavelength

11. Interference The interaction between waves is called When waves interact so that they add to make a larger wave it is called waves are

12. Interference The interaction between waves is called interference When waves interact so they cancel each other it is called waves are

13. Diffraction When traveling waves encounter an obstacle or opening in a barrier that is about the same size as the wavelength, they bend around it – this is called

14. Diffraction When traveling waves encounter an obstacle or opening in a barrier that is about the same size as the wavelength, they bend around it – this is called diffraction traveling particles do not diffract The diffraction of light through two slits separated by a distance comparable to the wavelength results in an interference pattern of the diffracted waves An interference pattern is a characteristic of all light waves

15. 2-Slit Interference

16. The Photoelectric Effect It was observed that many metals emit electrons when a light shines on their surface this is called the Classic wave theory attributed this effect to the light energy being transferred to the electron According to this theory, if the wavelength of light is made shorter, or the light waves’ intensity made brighter, more electrons should be ejected remember: the energy of a wave is directly proportional to its amplitude and its frequency this idea predicts if a dim light were used there would be a lag time before electrons were emitted to give the electrons time to absorb enough energy

17. Experiments showed that there was called the It was also observed that high-frequency light from a dim source caused electron emission The Photoelectric Effect: The Problem

18. Einstein’s Explanation Einstein proposed that the light energy was The energy of a photon of light is the proportionality constant is

19. Calculate the number of photons in a laser pulse with wavelength 337 nm and total energy 3.83 mJ What is the frequency of radiation required to supply 1.0 x 10 2 J of energy from 8.5 x 10 27 photons?

20. Ejected Electrons One photon at the threshold frequency gives the electron just enough energy for it to escape the atom When irradiated with a shorter wavelength photon, the

21. 1.No electrons would be ejected. 2.Electrons would be ejected, and they would have the same kinetic energy as those ejected by yellow light. 3.Electrons would be ejected, and they would have greater kinetic energy than those ejected by yellow light. 4.Electrons would be ejected, and they would have lower kinetic energy than those ejected by yellow light. Suppose a metal will eject electrons from its surface when struck by yellow light. What will happen if the surface is struck with ultraviolet light?

22. Spectra When atoms or molecules absorb energy, that energy is often released as light energy fireworks, neon lights, etc. When that emitted light is passed through a prism, a pattern of particular wavelengths of light is seen that is unique to that type of atom or molecule – the pattern is called an

23. The Bohr Model of the Atom The energy of the atom is ______________, and the amount of energy in the atom is related to the electron’s position quantized means The electron’s positions within the atom (______________) are called stationary states Each state is associated with a fixed circular orbit of the electron around the nucleus. The higher the energy level, ________________________________ The first orbit, ______________________________________________ The atom changes to another stationary state only by absorbing or emitting a photon. Photon energy (h ) equals the difference between two energy states.

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25. Bohr Model of H Atoms

26. Emission Spectra

27. Which is a higher energy transition? 6  5 or 3  2 5  3 or 3  1 2  3 or 3  4

28. Rydberg’s Spectrum Analysis Rydberg developed an equation involved an inverse square of integers that could describe the spectrum of hydrogen. What is the wavelength (nm) of light based on an electron transition from n = 4 to n = 2?

29. Wave Behavior of Electrons de Broglie proposed that particles could have wave-like character Predicted that the wavelength of a particle was inversely proportional to its momentum Because an electron is so small, its wave character is significant

30. What is the wavelength of an electron traveling at 2.65 x 10 6 m/s. (mass e - = 9.109x10 -31 kg) Determine your wavelength if you are walking at a pace of 2.68 m/s. (1 kg = 2.20 lb)

31. The matter-wave of the electron occupies the space near the nucleus and is continuously influenced by it. The Schrödinger wave equation allows us to solve for the energy states associated with a particular atomic orbital. The square of the wave function (   ) gives the probability density, The Quantum Mechanical Model of the Atom

32. Probability & Radial Distribution Functions  2 is the probability density The Radial Distribution function represents the total probability at a certain distance from the nucleus Nodes in the functions are where

33. Probability Density Function The probability density function represents the total probability of finding an electron at a particular point in space

34. Radial Distribution Function The radial distribution function represents the total probability of finding an electron within a thin spherical shell at a distance r from the nucleus The probability at a point decreases with increasing distance from the nucleus, but the volume of the spherical shell increases The net result is a plot that indicates the most probable distance of the electron in a 1s orbital of H is 52.9 pm

35. Solutions to the Wave Function,  Calculations show that the size, shape, and orientation in space of an orbital are determined to be three integer terms in the wave function These integers are called

36. Principal Quantum Number, n Characterizes the energy of the electron in a particular orbital and ______________________________ corresponds to Bohr’s energy level n can be The larger the value of n, As n gets larger, Energies are defined as being negative an electron would have E = 0 when it just escapes the atom

37. The energies of individual energy levels in the hydrogen atom (and therefore the energy changes between levels) can be calculated. What is the energy of a photon of light based on an electron transition from n = 4 to n = 2? Principal Quantum Number, n

38. Principal Energy Levels in Hydrogen

39. Angular Momentum Quantum Number, l The angular momentum quantum number determines the _____________________________________ l can have ________________________________ Each value of l is called by a particular letter that designates the shape of the orbital ____________ orbitals are spherical ____________ orbitals are like two balloons tied at the knots ____________orbitals are mainly like four balloons tied at the knot ____________ orbitals are mainly like eight balloons tied at the knot principal (n) quantum numberpossible angular momentum (l) quantum number(s) 1 2 3 4 5

40. Magnetic Quantum Number, m l The magnetic quantum number is an integer that specifies the the direction in space the orbital is aligned relative to the other orbitals Values are Gives the number of orbitals of a particular shape when l = 2,

41. l = 0, the s orbital Each principal energy level has one s orbital _________________orbital in a principal energy state Number of nodes = (n – 1)

42. l = 1, p orbitals Each principal energy state Each of the three orbitals points along a different axis p x, p y, p z 2 nd lowest energy orbitals in a principal energy state Two-lobed One node at the nucleus, total of n nodes

43. l = 2, d orbitals Each principal energy state above Four of the five orbitals are aligned in a different plane the fifth is aligned with the z axis, 3 rd lowest energy orbitals in a principal energy level Mainly four-lobed one is two-lobed with a toroid Planar nodes higher principal levels also have spherical nodes

44. l = 2, d orbitals

45. l = 3, f orbitals Each principal energy state above 4 th lowest energy orbitals in a principal energy state Mainly eight-lobed some two-lobed with a toroid Planar nodes higher principal levels also have spherical nodes

46. l = 3, f orbitals

47. Quantum Numbers: n, l, m l

48. Quantum Numbers Give the name, magnetic quantum numbers, and number of orbitals for each sublevel with the following quantum numbers: (a) n = 3, l = 2 sublevel name possible m l values number of orbitals (b) n = 2, l = 0 (c) n = 5, l = 1 (d) n = 4, l = 3