Hybridization II

For any molecule given, you should be able to provide:

• a Lewis structure (knowing the Lewis, you can predict the expected shape and then the type of hybridization involved)
• a 3-D structural representation (including -name, bond angle, molecular dipole)
• an energy level diagram using valence electrons to show hybrid orbital formation and final bonding
• an orbital sketch (include sigma and pi bonds)

From today, you should have done all of the above for:

BH3 PCl3 N2H4 HCN C2Br2 CH2O C2Br4 CH3CH=CH2

[A happy thought to end this puppy today. Why was the polar bear not white anymore. Asnwer: Because it was tickled pink.)

Hybridization

"If you know the shape, then you know the type of hybridization."

Hybridization maximizes orbital overlap. Hybridization provides the electron densities with the maximum separation. Without hybridization, measured bond angles (ex. 109.5 of tetrahedral) would conflict with predicted 90 of p-orbitals of valence bond theory without hybridization.

The link below reviews the common shapes, briefly overviews hybridization then provides a 'flow chart' to help connect central attributes (atoms attached & lone pairs) to the type of hybridization. At the bottom of the page are some sample questions. If you construct the Lewis structure for each, you should be able to identify the hybridization type and then the bond angle.
http://misterguch.brinkster.net/VSEPR.html

Once the last hybridization lesson is given, for any molecule you should be able to:

• draw its Lewis structure
• draw a 3-D representation (include bond angle, shape name, polarity of bonds & overall dipole of molecule)
• use energy level diagrams to show required hybridization of central atom
• provide a labeled* orbital sketch of the bonding [*sp3/sp2/sp & pi/sigma bonds]

From today you were asked to complete energy level diagrams and orbital sketches for both CHCl3 and NF3 , plus the questions on page 235 (11-14)

[I am a little pressed for time this afternoon, so I am going to fall back on the old polar jokes. Ready? What's the difference between a polar bear and a panda? {Answer: About 2500 kilometers. another? Where do polar bears keep their money? In snow banks.]

[Still looking for the link to explain bond angle measuring. :<]

Valence Bond Theory

• as the name valence bond theory implies, it is the theory of bonding on a valence (electron) level
• a bond: the overlap of an orbital with a single electron with another orbital with a single electron


• the resulting bond orbital contains 2 electrons of opposite spin

From today: p232 (1 to 5; with #4 provide both energy level & orbital sktech for each molecule) and complete the hybridization preparation handout

At this point you should be able to represent bonding in terms of (1) Lewis structure (2) 3-D shape (3) energy level diagram and (4) orbital sketch

There are a few issues with VBT as it has been described so far...

Considered the conflict between bond angles as indicated by the VBT depiction of H2O compared to the VSEPR bond angles. The link below will address the bond angle conflict as well as look ahead at hybridization.

http://www.sparknotes.com/testprep/books/sat2/chemistry/chapter4section9.rhtml

The above link is an SAT test preparation site. Have a look around the site for other interesting gems.

I am running out of time for today. I shall leave you with another polar [bear] joke: Why do polar bears win so many races? Answer: Because they are always in the "pole" position. Another question : Where will Woody be tomorrow?

Polar Molecules

Today was about polar molecules.

1. Draw Lewis structure - use the rules!
2. Consider the central atom, based upon the number of attached atoms and number of lone electron pairs predict the 3-D shape [see shape link below step #3]
3. Using the 3-D shape, identify all bonds as polar/nonpolar; if polar bonds exist - take into account their relative position to one another - do they polar forces cancel?

shape link: http://www.webchem.net/notes/chemical_bonding/shapes_of_molecules.htm

For CH4 SO3 PCl3 SBr2 and SF2 you were asked to draw a Lewis structure, 3-D structure and identify the polarity of the molecule

In addition for p230 4abcg you were to provide 3-D structures and identify polarity of the molecule

A few polar molecule links:

http://preparatorychemistry.com/Bishop_molecular_polarity.htm

http://www.ausetute.com.au/molpolar.html

And one that goes over electron configuration type stuff [Hey, isn't there a quiz coming up soon?]

http://www.webchem.net/notes/atomic_structure/electron_configuration.htm

[If you click the AS Chemistry tab, then chemical bonding, then breaking the octet - you shall find some interesting info. Looking at other information under the AS Chemistry Tab yields many other gems as well. :<]

[In honour of all of this talk about polar bonds, I leave you with the following: What do you call polar bears when they get caught in the rain? answer: drizzly bears. :<)

electronegativity & breaking the octect

Good day reader.



What is electronegativity and how do you use the periodic table to determine an atom's electronegativity?



Breaking the octet.

The octect can be broken. H does not obey the octet. B does not obey the octet. Be does not obey the octet. Those are the 'traditional' exceptions [exclusions] - from the octet rule. Other elements can be excluded from the octet as well. P for example.



As we shall see later this unit. The bonding that is considered involves the s and p orbitals. Though sometimes the s and p are not enough. In the orbital world, what letter comes after s and p...?



sp3d* and sp3d2* provide additional room. Remember the word hybridization - it will came up in another few days. In the mean time did you check out the links from yesterday? The sparknote link has a few additional tidbits of explorable information.



*[At this point the sp3d and sp3d2 may be unknown, but soon the mist will clear, the sun will break out in all of its full colour spectrum [using high resolution spectroscopy of course] glory.



Demo time is soon. Have you searched for your demo yet?



[Why do white bears dissolve in water? Ans: Because they are polar.] [What is white, furry and goes RRRRG! RRRRG! Ans: A polar bear going backwards]

Molecular Shapes

Coming soon to a lesson near you- molecular shapes.

Do you remember the basic shapes? Their bond angles? 3-D depiction of each?

• linear
• trigonal planar
• tetrahedral
• trigonal pyramidal
• angular (bent)

If you answered with a resounding "Yes!" to the above 3 questions and you could picture in your head all of the basic shapes. Good for you!

Maybe one of the links below will refresh your memory some more?

http://www.sparknotes.com/testprep/books/sat2/chemistry/chapter4section8.rhtml

http://www.ausetute.com.au/shapemol.html

They both go beyond our requirements as it also includes trigonal bipyramidal [sp3d] *and octahedral [sp3d2]*. However, the sparknotes site does discuss hybridization - a soon coming-up chem*is*try concept.

[Why is there a brick above the blackboard at the front of the classroom? Does anyone read these little puppies?]

*[What is this sp3d and sp3d2 of which you type? Again does anyone read this stuff and thus ask about it? Hmmm, I wonder?]

Quantum Numbers

Such a large topic. So many things that one could ask about it. And yet, it deals with such small particles. Does that even seem fair?

Question: Which of the following sets of quantum numbers are valid? If they are valid, state the possible orbitals that are described. If the quantum number set is invalid, what is incorrect in the set?

(a) {2,0,0,+1/2} (b) {3,1,-1,-1/2} (c) {2,2,1,+1/2} (d) {3,2,-3,-1/2}


Question: Which quantum number distinguishes between the s, p, d and f? The value for each?

Question: What is the orbitial significance of: m=+2,+1,0-1,-2 ?

These questions get posted, but where are the answers? If you, the reader, answers the questions, how will you know that you are correct? Will anyone ask and/or answer these last few questions? Well, anyone?
[Since the comment option is not available, what else can be done? Hmmm.... :<]

Tomorrow's possible topic: Heisenberg [At this typing, this blogger is uncertain. Ha ha :<]

Did you hear the one about the chemist was reading a book on helium and just couldn't put it down?