1. Sydney Opera House Opens (1973) READING: Chapter 8 sections 1 – 2 READING: Chapter 8 sections 1 – 2 HOMEWORK – DUE TUESDAY 10/20/15 HOMEWORK – DUE TUESDAY 10/20/15 HW-BW 7.1 (Bookwork) CH 7 #’s 5, 7-12 all, 14, 15, 20, 21, 24, 28-31 all, 34 HW-BW 7.1 (Bookwork) CH 7 #’s 5, 7-12 all, 14, 15, 20, 21, 24, 28-31 all, 34 HW-WS 12 (Worksheet) (from course website) HW-WS 12 (Worksheet) (from course website) HOMEWORK – DUE THURSDAY 10/22/15 HOMEWORK – DUE THURSDAY 10/22/15 HW-BW 7.2 (Bookwork) CH 7 #’s 39, 42, 48-52 all, 55-60 all, 64, 69, 71, 72, 78, 90 HW-BW 7.2 (Bookwork) CH 7 #’s 39, 42, 48-52 all, 55-60 all, 64, 69, 71, 72, 78, 90 HW-WS 13 (Worksheet) (from course website) HW-WS 13 (Worksheet) (from course website) Lab Lab Wednesday/Thursday – EXP 10 Wednesday/Thursday – EXP 10 Prelab Prelab Bring a computer if you have one Bring a computer if you have one Next Monday/Tuesday – Open office hour Next Monday/Tuesday – Open office hour Next Wednesday/Thursday – EXP 11 Next Wednesday/Thursday – EXP 11 Prelab Prelab

2. Ejected Electrons One photon at the threshold frequency gives the electron just enough energy for it to escape the atom One photon at the threshold frequency gives the electron just enough energy for it to escape the atom binding energy,  binding energy,  When irradiated with a shorter wavelength photon, the electron absorbs more energy than is necessary to escape When irradiated with a shorter wavelength photon, the electron absorbs more energy than is necessary to escape This excess energy becomes kinetic energy of the ejected electron This excess energy becomes kinetic energy of the ejected electron Kinetic Energy = E photon – E binding KE = h − 

3. 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. 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?3

4. Spectra When atoms or molecules absorb energy, that energy is often released as light energy When atoms or molecules absorb energy, that energy is often released as light energy fireworks, neon lights, etc. 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 emission spectrum 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 emission spectrum non-continuous non-continuous can be used to identify the material can be used to identify the material

5. Examples of Spectra

6. The Bohr Model of the Atom The energy of the atom is quantized, and the amount of energy in the atom is related to the electron’s position The energy of the atom is quantized, and the amount of energy in the atom is related to the electron’s position quantized means that the atom could only have very specific amounts of energy quantized means that the atom could only have very specific amounts of energy The electron’s positions within the atom (energy levels) are called stationary states The electron’s positions within the atom (energy levels) are called stationary states Each state is associated with a fixed circular orbit of the electron around the nucleus. Each state is associated with a fixed circular orbit of the electron around the nucleus. The higher the energy level, the farther the orbit is from the nucleus. The higher the energy level, the farther the orbit is from the nucleus. The first orbit, the lowest energy state, is called the ground state. The first orbit, the lowest energy state, is called the ground state. The atom changes to another stationary state only by absorbing or emitting a photon. The atom changes to another stationary state only by absorbing or emitting a photon. Photon energy (h ) equals the difference between two energy states. Photon energy (h ) equals the difference between two energy states.

7. The Bohr Model of the Atom

8. Bohr’s Model The electrons travel in orbits that are at a fixed distance from the nucleus The electrons travel in orbits that are at a fixed distance from the nucleus therefore the energy of the electron was proportional to the distance the orbit was from the nucleus therefore the energy of the electron was proportional to the distance the orbit was from the nucleus Electrons emit radiation when they “jump” from an orbit with higher energy down to an orbit with lower energy Electrons emit radiation when they “jump” from an orbit with higher energy down to an orbit with lower energy the emitted radiation was a photon of light the emitted radiation was a photon of light the distance between the orbits determined the energy of the photon of light produced the distance between the orbits determined the energy of the photon of light produced

9. Quantum Mechanical Explanation of Atomic Spectra Each wavelength in the spectrum of an atom corresponds to an electron transition between orbitals Each wavelength in the spectrum of an atom corresponds to an electron transition between orbitals When an electron is excited, it transitions from an orbital in a lower energy level to an orbital in a higher energy level When an electron is excited, it transitions from an orbital in a lower energy level to an orbital in a higher energy level When an electron relaxes, it transitions from an orbital in a higher energy level to an orbital in a lower energy level When an electron relaxes, it transitions from an orbital in a higher energy level to an orbital in a lower energy level When an electron relaxes, a photon of light is released whose energy equals the energy difference between the orbitals When an electron relaxes, a photon of light is released whose energy equals the energy difference between the orbitals

10. Electron Transitions To transition to a higher energy state, the electron must gain the correct amount of energy corresponding to the difference in energy between the final and initial states To transition to a higher energy state, the electron must gain the correct amount of energy corresponding to the difference in energy between the final and initial states Electrons in high energy states are unstable and tend to lose energy and transition to lower energy states Electrons in high energy states are unstable and tend to lose energy and transition to lower energy states Each line in the emission spectrum corresponds to the difference in energy between two energy states Each line in the emission spectrum corresponds to the difference in energy between two energy states

11. 12345

13. Emission Spectra

15. Bohr Model of H Atoms

16. Emission Spectra

17. Hydrogen Energy Transitions

20. 1234 5 6 Which is a higher energy transition? 6  5 or 3  2 5  3 or 3  1 2  3 or 3  4

21. Rydberg’s Spectrum Analysis Rydberg developed an equation involved an inverse square of integers that could describe the spectrum of hydrogen. 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? HUH?!?!?

22. Wave Behavior of Electrons de Broglie proposed that particles could have wave-like character de Broglie proposed that particles could have wave-like character Predicted that the wavelength of a particle was inversely proportional to its momentum Predicted that the wavelength of a particle was inversely proportional to its momentum Because an electron is so small, its wave character is significant Because an electron is so small, its wave character is significant h = planks constantm = mass of particlev = velocity

23. What is the wavelength of an electron traveling at 2.65 x 10 6 m/s. (mass e - = 9.109x10 -31 kg)

24. Determine your wavelength if you are walking at a pace of 2.68 m/s. (1 kg = 2.20 lb)

25. 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, a measure of the probability of finding an electron of a particular energy in a particular region of the atom. The Quantum Mechanical Model of the Atom

26. Probability & Radial Distribution Functions  2 is the probability density  2 is the probability density the probability of finding an electron at a particular point in space the probability of finding an electron at a particular point in space decreases as you move away from the nucleus decreases as you move away from the nucleus The Radial Distribution function represents the total probability at a certain distance from the nucleus The Radial Distribution function represents the total probability at a certain distance from the nucleus maximum at most probable radius maximum at most probable radius Nodes in the functions are where the probability drops to 0 Nodes in the functions are where the probability drops to 0

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

28. 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

29. 2s and 3s 2s n = 2, l = 0 3s n = 3, l = 0 Tro: Chemistry: A Molecular Approach, 2/e

30. 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 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 quantum numbers These integers are called quantum numbers principal quantum number, n principal quantum number, n angular momentum quantum number, l angular momentum quantum number, l magnetic quantum number, m l magnetic quantum number, m l

31. Principal Quantum Number, n Characterizes the energy of the electron in a particular orbital and the size of that orbital Characterizes the energy of the electron in a particular orbital and the size of that orbital corresponds to Bohr’s energy level corresponds to Bohr’s energy level n can be any integer  1 n can be any integer  1 The larger the value of n, the more energy the orbital has The larger the value of n, the more energy the orbital has The larger the value of n, the larger the orbital The larger the value of n, the larger the orbital Greater relative distance from the nucleus Greater relative distance from the nucleus As n gets larger, the amount of energy between orbitals gets smaller As n gets larger, the amount of energy between orbitals gets smaller Energies are defined as being negative Energies are defined as being negative an electron would have E = 0 when it just escapes the atom an electron would have E = 0 when it just escapes the atom

32. The energies of individual energy levels in the hydrogen atom (and therefore the energy changes between levels) can be calculated. 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

33. Principal Energy Levels in Hydrogen

34. Angular Momentum Quantum Number, l The angular momentum quantum number determines the shape of the orbital The angular momentum quantum number determines the shape of the orbital l can have integer values from 0 to (n – 1) l can have integer values from 0 to (n – 1) Each value of l is called by a particular letter that designates the shape of the orbital Each value of l is called by a particular letter that designates the shape of the orbital s (spherical) orbitals are spherical s (spherical) orbitals are spherical p (principal) orbitals are like two balloons tied at the knots p (principal) orbitals are like two balloons tied at the knots d (diffuse) orbitals are mainly like four balloons tied at the knot d (diffuse) orbitals are mainly like four balloons tied at the knot f (fundamental) orbitals are mainly like eight balloons tied at the knot f (fundamental) orbitals are mainly like eight balloons tied at the knot principal (n) quantum numberpossible angular momentum (l) quantum number(s) 10 (s) 20, 1 (s, p) 30, 1, 2 (s, p, d) 40, 1, 2, 3 (s, p, d, f) 50, 1, 2, 3, 4 (s, p, d, f, g)

35. Magnetic Quantum Number, m l The magnetic quantum number is an integer that specifies the orientation of the orbital The magnetic quantum number is an integer that specifies the orientation of the orbital the direction in space the orbital is aligned relative to the other orbitals the direction in space the orbital is aligned relative to the other orbitals Values are integers from −l to +l Values are integers from −l to +l including zero including zero Gives the number of orbitals of a particular shape Gives the number of orbitals of a particular shape when l = 2, the values of m l are −2, −1, 0, +1, +2; which means there are five orbitals with l = 2 when l = 2, the values of m l are −2, −1, 0, +1, +2; which means there are five orbitals with l = 2