1.  and  Bonds MO Theory

2. Visit: https://checkin.ics.uci.edu/https://checkin.ics.uci.edu/ Site is down, so there is no word of the day Visit: https://learningcatalytics.com/https://learningcatalytics.com/ Sign in MasteringChemistry account name When prompted, type session ID: 87317647 Please turn off all downloads. You can usually pause them by clicking on them and clicking pause. Facebook and youtube are officially banned during class time (this is not me micromanaging, it’s a legit internet issue as told to me by OIT). Remember back 5 rows of even side are no seating zones Word of the day site is down: Don’t do today. LearningCatalytics: session ID: 87317647

3. ANSWERING QUESTIONS Review Question: How do you know when to move the order of the elements when listing the ionization energy? Does one of them have a stable electron configuration (half filled or fully filled)? Why does the anti bonding orbital has an additional node between the nuclei and is called the pi*2p orbital? Are nodes and lobes the same thing? Word of the day site is down: Don’t do today. LearningCatalytics: session ID: 87317647

4. MO THEORY: S ORBITALS E isolated H atoms Bonding MO, σ 1s Anti-bonding MO, σ * 1s 1s - 1s 1s + 1s  s orbitals form  and  * molecular orbitals  Add and subtract orbitals to get the bonding and anti-bonding orbitals  Start with 2 atomic s orbitals end with 2 molecular orbitals.  Fill in electrons from low to high energy, just like in atomic orbital diagrams Word of the day site is down: Don’t do today. LearningCatalytics: session ID: 87317647

5. MO THEORY: P ORBITALS End to end overlap Side to side overlap  p orbitals form  and  * molecular orbitals or  and  * orbitals depending on type of overlap  Add and subtract orbitals to get the bonding and anti-bonding orbitals  Start with 6 atomic orbitals end with 6 molecular orbitals  Fill in electrons from low to high energy, just like in atomic orbital diagrams Word of the day site is down: Don’t do today. LearningCatalytics: session ID: 87317647

6. PRACTICE Draw the molecular orbital diagram for nitrogen. Is it paramagnetic or diamagnetic? What is the bond order? Hint: ½(bonding electron-antibonding electrons) What would happen to the bond order if you added an electron? The bond length? What would happen to the bond order if you subtracted an electron? The bond length? E Diamagnetic Bond Order: ½(8-2)=3 Adding electron: adds to antibonding orbital so it would subtract from the bond order making it longer. subtracting electron: subtracts from bonding orbital, lowering bond order, making the bond longer NN 2p N2N2 Word of the day site is down: Don’t do today. LearningCatalytics: session ID: 87317647

7. PRACTICE Draw the molecular orbital diagram for fluorine. Is it paramagnetic or diamagnetic? What is the bond order? Hint: ½(bonding electron-antibonding electrons) What does adding an electron do to the bond order? To the bond length? What does subtracting an electron do to the bond order? To the bond length? E diamagnetic Bond Order: ½(8-6)=1 Adding electron: adds to antibonding orbital so it would subtract from the bond order making the bond longer. subtracting electron: subtracts from an anti-bonding orbital, increasing the bond order, making the bond shorter Word of the day site is down: Don’t do today. LearningCatalytics: session ID: 87317647

8. PRACTICE The ground-state electron configuration of the ion C 2 n- is  2s 2  2s *2  2p 4  2p 2. What is the charge on the anion? Draw the MO diagram. Is it paramagnetic or diamagnetic? What is the bond order? Hint: ½(bonding electron-antibonding electrons) Would adding an electron add or subtract from the bond order? Would subtracting an electron make the bond longer or shorter? Charge= -2 Carbon 4+4=8 valence electrons is neutral 10 present so -2 charge E Diamagnetic Bond Order: ½(8-2)=3 Adding electron: adds to antibonding orbital so it would subtract from the bond order subtracting electron: subtracts from bonding orbital, lowering bond order, making the bond longer C-C- C-C- C 2 2- 2p Word of the day site is down: Don’t do today. LearningCatalytics: session ID: 87317647

9. Heteronuclear Practice For CN the energy of the molecular orbitals follows the order of carbon (a.k.a.  2p <  2p ) Draw the MO diagram. Give the valence shell electron configurations of CN and CN -. Are they paramagnetic or diamagnetic? Tell the bond order of each. Which has the stronger bond? E CN CN E CN CN -  2s 2  2s *2  2p 4  2p 1  2s 2  2s *2  2p 4  2p 2 paramagnetic diamagnetic Bond order= ½ (7-2)=2.5 Bond order= ½ (8-2)=3 Stronger! 2p Word of the day site is down: Don’t do today. LearningCatalytics: session ID: 87317647

10. PRACTICE Consider the hypothetical species HeH. What charge, if any, should be present on this combination of atoms to produce the most stable molecule or ion possible? Draw the MO diagram for the neutral species first. Decide what ion gives largest bond order What is the bond order on the neutral species and what bond order, if changed, is on the ion you chose? He H HeH Neutral B.O.= ½(2-1)=0.5 Maximum bond order if you remove electron from antibonding orbital. Gives +1 ion Word of the day site is down: Don’t do today. LearningCatalytics: session ID: 87317647

11. PRACTICE If the charge on the neutral species were increased or decreased by one what would be the affect on the bonding of the atom. If the charge on the species you chose were increased or decreased by one what would be the affect on the bonding of the atom. He H HeH +1 B.O.= ½ (2)=1 He H HeH Neutral B.O.= ½(2-1)=0.5 Neutral: If charge was increased: remove from antibonding giving higher bond order. If charge decreased: add electron to antibonding giving lower bond order. +1: If charge was increased: remove from bonding giving lower bond order. If charge decreased: add electron to antibonding giving lower bond order. Word of the day site is down: Don’t do today. LearningCatalytics: session ID: 87317647