Chem Discussion #12 Chapter 8 and 10 Your name/ TF s name: Discussion Day/Time:

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1 Chem 0 06 Discussion # Chapter 8 and 0 Your name/ TF s name: Discussion Da/Time: En = -R Things ou should know when ou leave Discussion toda for one-electron atoms: Z n = J Z n = -.6eV ΔEmatter=En-Em ; Ionization Energ=E En(initial) ΔΕlight=hνlight= IE +KE. Consider the following energ levels of the hdrogen atom as shown below in the diagram: a. What are the two energ levels involved in the ionization energ of an electron from H in the ground state? Z n b. What is the ground state H atom ionization energ in J, ev and kj/mol? (H(g) H + (g) + e - ) c. What is the expression for the ionization energ of an electron from the n= state of an atom with atomic number Z?. An electron is ionized from the ground state of an atom, with E = J, b light with frequenc Hz. What is the kinetic energ (in ev) of the ejected electron?

2 . The light with wavelength of 65 nm will ionize H atom in the n = energ level. What effect will light with wavelength = 657 nm have? (Choose all that appl) a. Atom will be transparent to the light of this wavelength. b. Ionization will take place c. Ionization will not take place d. The ionized electron will use excess energ for kinetic energ 4. The light with wavelength of 65nm will ionize H atom in the n = energ level. What effect will light with wavelength = 65nm have? (Choose all that appl) a. Atom will be transparent to the light of this wavelength. b. Ionization will take place c. Ionization will not take place d. The ionized electron will use excess energ for kinetic energ 5. The photoelectric effect threshold frequenc of a metal is υ0 = *0 5 Hz. Gamma radiation of frequenc * 0 7 Hz ejects electrons from the metal. Which of the following occurs when the intensit of the gamma radiation is reduced b 50 %? a. The velocit of the ejected electrons will be reduced b a factor of two. b. The kinetic energ of the ejected electrons will be reduced b a factor of two. c. The kinetic energ of the ejected electrons will be reduced b a factor of four. d. Kinetic energ and the velocit of the ejected electrons will sta the same. e. Number of ejected electrons will increase. f. Number of ejected electrons will decrease. 6. Assume light is able to eject electrons from a metal. What do ou expect as the wavelength of the light is increased? a. If the light wavelength reaches the lowest, electrons will no longer be ejected. b. Electrons will still be ejected but the will move faster and faster. c. Electrons will still be ejected but the will move slower and slower. d. More and more electrons will be ejected but the will have the same kinetic energ. e. More information needed. 7. The work function (ionization energ), of chromium metal is 7.x0-9 J. What is the maximum kinetic energ of an electron, if it is ejected from chromium metal b light of wavelength 50.nm? a. What will happen to the speed and quantit of the ejected electrons if the wavelength of the light will increase? b. What will happen to the speed and quantit of the ejected electrons if the wavelength of the light will decrease? c. What will happen to the speed and quantit of electrons if the intensit of the light will increase?

3 Things ou should know when ou leave Discussion toda. Atomic wave function famil album a. Principle quantum number n=,,, specifies energ level n= j+l b. Number of nodal planes (l). c. Angular momentum quantum number (l=0,,, n-) defines the shape of the orbital. d. ml= -l,.0 l e. Number of loops j (j=n-l) f. S, P and D and F orbitals. g. Size of the orbital is proportional to n Electron configuration a. Orbital, Shell, Subshell b. Shielding c. Pauli Exclusion Principle. Auf-bau. Hund s rule Periodic Trends (I.E., E.A., Radius, Ionic Radius, Electronegativit) For man electron atoms: Zeff 8 Zeff kj Zeff En.6(eV).8 0 (J) n n mol n Useful Information Below dx, dx - and dz orbital. Be sure to correctl orient our orbitals in the x--z space.

4 Orbital l n=j+l j= n-l Shape Number of orbitals in a subshells(ml) l+ s 0 p d etc 4 etc 4 etc j=n j=n- j=n- Sphere Dumbbell orientation in space # e - that can fit 6 Cloverleaf 5 0 f 4 5 etc j=n For the two hdrogen electron clouds below identif the quantum number n, the quantum number l, the number of radial loops j, and the specific name of the orbital (ou must indicate orientation, e.g. dx). A z n = l= j= n = l= j= z x x name: name: a. For the two hdrogen electron clouds above, which has the largest ionization energ? (Note: in H atom, all orbitals of same n have the same energ.) b. Match each of the electron clouds above to one corresponding electron cloud cross section below. Indicate our answer b putting in the box next to the function.(x axis is distance from the nucleus, and axis is a probabilit of finding an electron at the given distance) 4

5 Probabilit. Fill out the table: n, l, j Name the orbital Draw the orbital n=, l=0 n=4, l= n=, l= n=, l= l=, j= l=0, j=. Complete the table below about the hdrogen atom: Electron Cloud Name name = s Principle quantum number, n Angular momentum quantum number, l j (number of radial loops) n = l = j = name = n = l = j = name = n = l = j = Distance from Nucleus (A) name = n = 4 l = j = name = n = l = j = 6 5

6 4. What are the possible angular momentum quantum numbers for an orbital in the n=4 shell? How man degenerate orbitals are in the n= shell? What are the?(note: in H atom, all orbitals of same n have the same energ.) 5. The figure shows three H atom electron clouds. a. Which of the following H atom electron clouds has the largest ionization energ? b. Write down the numerical expression that when evaluated gives the value in ev of smallest ionization energ of these three clouds.( Answer: 0.85) Additional Practice problems: 8. What electron cloud energies account for the line corresponding to the wavelength 44 nm in the gas discharge spectrum for the Balmer series of H atoms? (In the Balmer series in each of the emission lines corresponds to a natural frequenc of the electron cloud resulting from the mixing of an electron wave with more than two loop with the electron wave with loop) A. Onl the n = cloud energ B. Onl the n = 4 cloud energ C. Onl the n = 5 cloud energ D. The n = and n = 4 cloud energies E. The n = and n = 5 cloud energies F. None of these. 9. Photons of energ.6ev=r are able to ionize H in its n = energ level. Are photons of this energ are able to ionize He + in its n = energ level? 0. The ionization wavelength of H atom in the n = energ level is 65 nm. Will light of this wavelength ionize He + in the n = level? 6

7 . An electron is ionized from the ground state of an atom, with E = 0 ev, b light for which a photon of light energ is 6 ev. What is the kinetic energ (in ev) of the ejected electron?. What is the expression for the energ in J for the ground state of an electron cloud in Li +? a. Calculate wavelength (in nm) of the light corresponding to the Li + electron cloud resulting from mixing a loop electron wave with a loop electron wave? (Answer:0). What is kinetic energ of the electron ionized from Li + in its n = 6 level b light of wavelength 0 nm?(answer: 0.94*0-9 ) 4. In terms of the variables ( like: R, h, and c) what is the smallest possible wavelength of light that will be emitted b a He + atom starting with the energ corresponding to level 6 loops? 5. What is the largest possible wavelength of light that will be emitted b be the Li + atom with the energ level corresponding to 6 loops? In preparation for lectures and next week discussion: 6. Draw the electron configuration diagram for C, but fill the diagram as if the C is in the ground state. Draw a dotted line around a shell. Circle a subshell. Draw a triangle around an orbital. Is C atom paramagnetic or diamagnetic? 8 Zeff a. Calculate Z eff of C, if IE = 086 kj/mol.(hint: IE= E -Einitial=.8 0 (J) ) n 7

8 Atom Z He Li Be 4 B 5 Electron configuration IE kj mol Zeff Trends in IE is Explained b: a. Z increases b. Electron electron repulsion c. New shell d. l increases or Zeff decreases (shielding) Ions (Ions Electron configuration) s 7 He + s s 50 s s 899 s px s Li + s Be + s s s 80 B + C 6 N 7 O 8 F 9 s p x p s 086 s px p pz C + s s px N + s s p x p O + s s px p pz s 680 F Ne Na s s p Mg [ Ne]s x p p z s 78 Ne + p p p s s x z Na + p p p s s x z Mg + [ Ne ]s Al [ ]s px Ne 578 Al + [ Ne ]s 8

9 Atom Z He Ions (Ions Electron configuration) Li Li + IE kj mol He + s 548 s Be 4 Be + B 5 s s B + 40 Zeff For the Ions Trends in IE is Explained b: a. Z increases b. Electron electron repulsion c. New shell d. l increases or Zeff decreases (shielding) C 6 C + s s px s s p x p N 7 N s s p p p O 8 O + F 9 x z F s s p p p Ne 0 Ne + x z s s p p p Na Na + x z Mg Mg + [ Ne ]s Al Al + [ Ne ]s 9

10 Exam answers:. a. qss>0 wss<o b. wss<o c. qss> J/gK. a. ΔrU < ΔrH b kJ/mol c. -0.5kJ/mol 4. C(graphite) + H (g) +0.5 O(g) CHOCH (l) 5. CH(g) C(g) +H(g) 6. a. -0kJ b. Less warm 7. Line : H(g) + N(g) Line N(g) +H(g) _A rh = fh(nh, g) none rh = fh(nh, g) + bh(n N) none rh = vaph(nh, g) B rh = bh(h H) + bh(n N) 8. 9kJ/mol 9. F,F,T,F 0. *0 9 photons/s. D. a. 5 energ levels b..ev c. No light is absorbed 0