ChChem 111L t 6Lecture 36

UMass Amherst Biochemistry Teaching Initiative...

Announcement • Final: Dec. 17th; 1:30pm – 3:30pm in Totman Gym

- No MakeupsN P id- No Pyramid

- Bring pencils, calculator, ID card and a good erasers

• Review Schedule - ISB 135Weds 4-6 PM C. JosephWeds 7-9 PM J Tyson and M JohnsonWeds 7 9 PM J. Tyson and M. JohnsonThurs 4-6 PM B.Botch

Offi H l T d f Fi l k• Office Hours only on Tuesday for Finals week

2...

Important !!• Final Conflict – Let me know by Saturday Night

3...

Homework• Finish Reading Chapter 9

O l H k• Owl Homework

4...

Recap• Internuclear Axis• Sigma (σ) bond

Pi ( ) b d• Pi (π) bonds• Multiple Bonds• Trans – Cis Isomers• MOT

5...

Bond Order (Using MOT)Bond order = ½ (# of bonding electrons - # of nonbonding electrons)

6...

Let’s PracticeDraw the molecular energy level diagram of He2

+? What is the bond order?

7...

MO of Li2Atomic orbitals must be of similar energy to form molecular orbitals.

Core electrons usually don’t do not contribute significantly to bonding in the molecule formation.

Li2 MO Configuration = (σ1s)2(σ∗1s)2(σ2s)2

8...

MO of Be2

Be2 MO Configuration = (σ1s)2(σ∗1s)2(σ2s)2(σ∗

2s)2

9...

Molecular orbitals from P orbitals

Note the amount they can mix and their relation to internucleari

10

axis

...

MO Diagram

11...

MOT P block

12...

Let’s practiceWh t i th B d O d O O O 2 O +What is the Bond Order O2, O2

-, O22-, O2

+

13...

MOT-Heteronuclear DiatomicsDifferences from Homonuclear case:• Electrons will be drawn to the more electronegative element .

Thus bonding orbitals will have more of that element characterThus bonding orbitals will have more of that element character and antibonding orbitals will have more character from the less electronegative element. As a result of having more A character the molecular orbital will• As a result of having more A character, the molecular orbital will be closer in energy to that elements atomic orbital.

14...