Chem Discussion #13 Chapter 10. Correlation diagrams for diatomic molecules. TF s name: Your name: Discussion Section:

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1 Chem Discussion #13 Chapter 10. Correlation diagrams for diatomic molecules. TF s name: Your name: Discussion Section: 1. Below is a plot of the first 10 ionization energies for a single atom in 3 rd row of the periodic table. The x- axis shows which ionization (e.g. IE1, IE2, etc) and the y-axis gives how much energy in MJ/mo a. What 3 rd row element does the plot show? b. First ionization energy IE 1 is 10.36eV calculate Z eff for that element. c. The arrow points to the jump between the 6 th and 7 th ionization energy. Which of the following statements are true? i. The number of protons (Z) changed. ii. The effective nuclear charge (Zeff) changed. iii. The quantum number n of the electron that is ionized changed. iv. The radius of the ion decreased 2. From the following neutral atom electron configurations, label the one with the highest third ionization energy, and lowest third ionization energy. Explain your answers. a. 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 b. 1s 2 2s 2 2p 6 3s 2 3p 6 4s 1 c.1s 2 2s 2 2p 6 3s 2 3p 6 3. Which one will have the greatest ionization energy? Na +, Ne, F -,O 2-4. ( at Home) Rank the following in terms of increasing ionization energy: Na, Li, B, N, Ne 5. ( at Home) Rank the following in terms of increasing ionization energy: Li +, B +, N +, Ne +, Na + 1

2 6. (at home) Write the ground state electron configuration for the following atoms and ions and determine if each is paramagnetic or diamagnetic: Al, Al 3+, V, V Answer the following questions about manganese (Mn): a. What is the electron configuration? b. Circle the letters corresponding to the picture of occupied electron clouds. ( Hint you need to know what are n, l, and j for one electron in each of the occupied electron clouds? A B C D E F G H I 2

3 a. For the pictures below fill in the empty boxes with corresponding names of the orbitals( 1s,2s,3s, 4s, 2p,3p,3d) b. Use the radial probability densities below (electron cloud cross section below ) to estimate the size of an atom of Mn. (Look at the x axis) 3

4 Things you should know when you leave Discussion today Atomic Orbital (s, p, d, f) vs. Molecular Orbital (σ, σ *, NB, π, π *, πnb) a. Total Number of MO =Total Number of AO Constructive and destructive interference (in phase and out-of-phase interaction) a. Sigma bond is achieved by head on overlap b. Bonding MO (σ, π) - Constructive interference in phase interaction c. Antibonding MO (σ *, π * ) - Destructive interference out-of-phase interaction d. π formed from side-by-side overlap of available p AO π * is out-of-phase overlap of available p AO π is in-phase side-by-side overlap of available p AO Factors that affect the formation of MOs from AOs: S.O.E. a. Symmetry AOs must have a compatible orientation to achieve an overlap. b.overlap: If AO's have correct symmetry, consider how much they overlap. The greater the overlap, the greater the energy change relative to the AO energies. c. Energy: If the pair of AO's has the correct symmetry and greatest overlap, consider relative AO energies. 4

5 1. If you have two atoms that together have 5 atomic orbitals, when those atoms combine to form a molecule, how many molecular orbitals are you going to have? 2. For each of the AO combinations below, draw the resulting MO. What do we call that resulting MO? a. Discuss any axes of symmetry the MO may have. b. Is this MO destructive or constructive interference (or neither or both)? c. (at home) Now draw as many other combinations of AOs that give, *, MOs as you can, using only s and p AOs. Discuss the relative energies of the resultant MOs you just drew. d. (at home ) Now draw as many other combinations of AOs that give, * MOs. 3. Which below describes the pairs of AO's in Li2 according to increasing overlap and why? a. 1s + 1s < 2s + 2s < 1s + 2s b. 1s + 2s < 1s + 1s < 2s + 2s c. 1s + 1s < 1s + 2s < 2s + 2s 5

6 4. Draw correlation diagram for He2 + : Keep in mind that: 1sσ* is more unstable than 1sσ is stable. a. What is the bond order of He2 +? ( Hint: useful information on page 9) b. Put in the order of increasing bond length H2; H2 + and He2 +. (hint : find the bond orders for all the molecules or molecular ions) 5. (at Home) Draw the correlation diagram for the HeH molecule. Which molecule or molecular ion will have the shortest bond HeH 3+,HeH 2+, HeH +, HeH, HeH -? 6. (at home) AO1 and AO2 are going to form MOs. Assume AO1 and AO2 have correct symmetry, greatest overlap, and are closest in energy. AO1 has IE = 7 ev and AO2 has IE = 9 ev. Draw a picture of this, clearly indicating the relative energies of all AOs and MOs. For each MO, discuss which AO contributes more to it. 6

7 7. (at home) AO1 and AO2 are going to form MOs. Assume AO1 and AO2 have correct symmetry, greatest overlap, and are closest in energy. AO1 has IE = 2 ev and AO2 has IE = 13 ev. Draw a picture of this, clearly indicating the relative energies of all AOs and MOs. For each MO, discuss which AO contributes more to it. 8. (at home) Look at the diagrams in questions 6 and 7. Which one represents compound with the most ionic characteristic? 9. Consider the Ionization energies for H, Na, and F. Assume z is along the bond axis. a. Draw the correlation diagram for NaF and HF: An Element: IE H 1s 13.6 ev F 2s 25.0 ev F 2pz 17.4 ev Na 3s 5.1eV b. Discuss the relative ionic and covalent character of NaF verses HF. [Hint: It might help if you look at the picture you just drew.] 7

8 c. Which pair of AOs in HF will interact most strongly? a. H 1s + F 1s b. H 1s + F 2s c. H 1s + F 2pz d. H 1s + F 2py e. C and D equally d. The bond pair in NaF is in the Na 3s + F 2pz MO. The bond pair in HF is in the H 1s + F 2pz MO. Which of the following is true? a. The bond pair is almost entirely on the F of HF b. The bond pair is almost entirely on the H of HF. c. The bond pair is almost entirely on the F of NaF. d. The bond pair is almost entirely on the Na of NaF e. (a) and (d) 10. Generally, the valence electrons on different atoms, rather than the core electrons, interact with one another. Choose the best explanation. a. Adjacent valence electron waves have the greatest overlap. b. Adjacent valence electron waves have the same energy. c. Core electron clouds have the wrong symmetry. d. Core electron clouds move with the wrong frequency. 11. When is the interaction of two AO orbitals most favored? General MO Correlation Diagram for second row in the Periodic table. 8

9 a. Bond Order: # of e in filled bonding orbitals # of e in filled antibonding orbitals BO.. 2 or B. O. # of filled bonding orbitals # of filled antibonding orbitals 1. Draw two AO energy diagrams for the atoms in CN - one atom on the left and one atom on the right, leaving space in the middle. Draw a picture of each AO. Draw the MO energy diagram and pictures of the resulting MOs in between and fill them with the electrons for the molecule. a. Draw the MO diagram(hint : count how many AO you start with and how many valence electrons you have) 9

10 b. Calculate the bond order. c. Is CN - diamagnetic or paramagnetic? d. Write the molecular electron configuration. e. Are the electrons centered more on C or on the N? f. If an electron is removed, will this make the bond longer or shorter? 2. (At home on a separate piece of paper) Draw two AO energy diagrams for the following atoms in [C2, N2, O2, F2, HF, BF, HB +, HO + ], one atom on the left and one atom on the right, leaving space in the middle. Draw a picture of each AO. Draw the MO energy diagram and pictures of the resulting MOs in between and fill them with the electrons for the molecule. a. Calculate the bond order for each molecule. b. Discuss which of the molecular orbitals are responsible for single, double bonds, etc. c. Discuss the relative length, reactivity and strength of these bonds. d. What are the magnetic properties of these molecules? (Which one is diamagnetic and which one is paramagnetic.) 10

11 Chem 101 Discussion #13 Chapter 10 TF s name: Your name: Discussion Section: Final Exam OPTIONAL review session s schedule: Thursday December 15. Session 1 10am-11:50pm Session2 1pm -2:50pm 1. Exam1, Exam 2, / Chapter2,3,4,5/ Dimensional analysis/ Stoichiometry/ Limiting Reagent CAS 203 / MS/IR / Intermolecular Forces/ 2. Chapter 6 /Vapor pressure/gas phase verses Liquid phase verses solid phase/ CAS 213 Chemical reactions/precipitation Reaction & Solubilit/ Acid-base, Redox /Molar calculations /Dimensional analysis/δvaph, ΔfusH/ /Heat capacity/solubility of Ionic compounds/ 3. Chapter 8/ Light and 1 electron system / emission /absorption/ Energy of a photon/ KE/ Ionization/Hydrogen Family Album /Multi-electron Atoms / Quantum Numbers / Electron Configuration/ Trends/ Shielding/ CAS MOs Chapter 10/ Multi-electron Atoms Lewis Structures / FC/ ON / Electron Configuration/ Trends/ Shielding/ CAS Chapter 7/Enthalpy/ First law/ calorimeter/ Exam 3 CAS