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LAB 20 Hybridization, Molecular Geometry & Polarity

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					LAB 1: Hybridization, Molecular Geometry & Polarity
BIOCHEMISTRY Procedure: 1. With your partner, draw the Lewis structures of methane (CH4). 2. Obtain a molecular model kit and make a model of your Lewis structures for CH4. To make the models start by placing the thick (lighter) grey bonds into the central atom and attaching the other atoms. Every bond must be attached to two plastic "atoms". If all the holes are filled, then the ball and stick model is done*. If holes are still open then remove one thick bond - a single bond and make a double bond between the two atoms. To make a double bond, you must use two flexible (darker) grey bonds. The molecule must have all the holes filled with bonds. When you disassemble the molecule, use the large white bond extractor when a bond is hard to remove. Rule 1: All holes must be filled, (except nitrogen – see note below) Rule 2: No triangles allowed!!! Color Code for MOLYMOD® Organic (student) Set: C = ebony (black); H = snow white; O = candy apple red; halogens = kelly green; N = sky blue (*leave one hole open); 3. After you make the model, check your Lewis structure (electron dot structures) with the model. The ball and stick model is the skeleton of the Lewis structure. The Lewis structure includes lone pairs of electrons (or unshared pairs or nonbonding electrons.) From the ball and stick model and the Lewis structure determine the number of sigma bond, pi bonds, lone pairs and hybridization for the central atom. For molecules that contain two or more central carbon atoms, pick one of the carbon atoms and analyze only that carbon atom. Do not try to describe the entire molecule’s shape. From the hybridization and the ball and stick model determine the electron pair geometry, the molecular geometry and the bond angle on the central atom or a center carbon atom. Does the ball and stick model match the Lewis structure? If it doesn't match you should check with your teacher. Next determine if there are any polar covalent bonds on the whole molecule. To do this use your periodic table to determine the electronegativity difference between all the bonds. If the electronegativity difference is less than ~0.4 for any and all bonds then the molecules is nonpolar. If there are any polar covalent bonds (electronegativity greater than 0.4) then you must next determine if the molecule is symmetrical or asymmetrical. A molecule is symmetrical if all the electron pairs around the center atom are the same. If the molecule is symmetrical then the molecule is nonpolar. If the molecule is asymmetrical (the center atom's electron pairs are different) then the molecule is also polar. In your lab notebook list the following for the CH4. - ball and stick model - number of lone pairs (LP)* - bond angle(s) - Lewis structure - hybridization* - polarity (polar or nonpolar) - # of sigma bonds* - electron pair geometry* - number of pi bonds* - molecular geometry* * - center atom or central carbon atom only

4.

5.

6.

7.

Repeat steps 2 – 6 using the following molecules. NH3 C2H6 H2O C2H4 CO2 C2H2 CCl4 CH2O

CH2O2 C6H6
(6 carbon ring alternating single and double bonds)

8.

EXTRA CREDIT: Make three different ball-and-stick models of C2H2Cl2. Show your teacher. Then determine the name for each. Use any source (CRC, biochemistry or organic text books, etc.)

CONCLUSION: 1. What is the connection between the hybridization, bond angle, and the electron pair geometry? 2. What is the difference between the electron pair geometry and the molecular geometry? Illustrate with an example(s). 3. What is the difference between a sigma () bond and a pi () bond? Using ethene (C2H4) as an example, make a sketch of each. 4. Determine the hybridization, electron pair geometry, molecular geometry and bond angles of the central atom for the following molecules. a. OCN5. 6. b. H2CO c. CHCl3 d. CO32-

Summarize how one determines if a molecule is a dipole. Use one of the molecules in question 4 to illustrate. Summarize what you learned during this lab.

________ ________

_______________________________ _______________________________

Hybridization, Molecular Geometry & Polarity
Purpose: Observations:

Ball & Stick

Lewis Structure

# of bonds of  bonds

# of LP Hybridation

Bond Angle Polarity (P or NP)

e- pair Geometry

Molecular geometry

CH4

NH3

H2O

CO2

CCl4

C2H6

C2H4

C2H2

CH4O

CH2O

CH2O2

C6H6

CONCLUSION: 1. What is the connection between the hybridization, bond angle, and the electron pair geometry?

2.

What is the difference between the electron pair geometry and the molecular geometry? Illustrate with an example(s).

3.

What are the four main differences between a sigma () bond and a pi () bond? Using ethene (C2H4) as an example, make a sketch of the electron distribution for a pi bond and a sigma bond.

4.

Determine the hybridization, electron pair geometry, molecular geometry and bond angles of the central atom for the following molecules and ions. OCNH2CO CHCl3 CO32-

Lewis Structure

Hybridization e- geometry
molecular geometry

bond angle

5.

Summarize how one determines if a molecule is a dipole. Use one of the molecules in question 4 to illustrate.

6.

Summarize what you learned. (Explain the concepts; do not make a list of what you learned.) This should be a well-written essay.

Extra Credit: Lewis Structure

IUPAC name

________ ________

_______________________________ _______________________________

Hybridization, Molecular Geometry & Polarity
Purpose: Observations: Center Atom Only

Ball & Stick

Lewis Structure

# of bonds # of L.P.

Hybridation Bond angle

e- pair Geometry Molecular geometry tetrahedron

Polarity

of  bonds

H

4 0
H

sp3 109.5 sp3 <109.5 (107) sp3 <109.5 (104.5) sp 180 sp3 109.5 sp3 109.5

CH4

H C H H
tetrahedron

NP

3 0 2 0 2 2

tetrahedron

NH3

H N H
trigonal pyramid

P

H

tetrahedron

H2O

H

O:

P
bent

:

linear

:

CO2

:O C O:
linear

:

NP

:Cl : : : : :

: 4 0 4 0

tetrahedron

CCl4

:Cl

C Cl :

NP
tetrahedron

:Cl :
H H

C2H6

H C C H H H
tetrahedron

:
tetrahedron

NP

H

H C C H

3 1 2

sp2 120 sp 180 sp3 109.5 sp2 120 sp2 120 sp2 120

trigonal planar

C2H4
H

NP
trigonal planar

linear

C2H2

H C C H
2
H
linear

NP

4 : : 0 3 : :

tetrahedron

CH4O

H C O H H
tetrahedron

P

H

trigonal planar

CH2O
H

C O

P 1
trigonal planar

H

3 1

trigonal planar

CH2O2

C O H O
H C C

: :

P
trigonal planar

: :
H

3
C H

trigonal planar

C6H6
CONCLUSION: 1.

H C C C H

NP 1
trigonal planar

H

What is the connection between the hybridization, bond angle, and the electron pair geometry?

2.

What is the difference between the electron pair geometry and the molecular geometry? Illustrate with an example(s).

3.

What is the difference between a sigma () bond and a pi () bond? Using ethene (C2H4) as an example, make a sketch of each.

4.

Determine the hybridization, electron pair geometry, molecular geometry and bond angles of the central atom for the following molecules and ions. OCNH2CO CHCl3 CO32-

Lewis Structure

Hybridization e- geometry
molecular geometry

bond angle

5.

Summarize how one determines if a molecule is a dipole. Use one of the molecules in question 4 to illustrate.

6.

Summarize what you learned.

Extra Credit: Lewis Structure

IUPAC name

Color key for wooden balls.(done by Mr. Dreon - that physics guy): C = ebony; H = maize; O = candy apple red; Cl (& F) = kelly green; N = sky blue; Be = snow white; Al = passionate pink; P = slate; S = copper; Br = pumpkin orange; I = grape. 7. Return all stick, springs and balls to their container in their original order that is outlined below (look at colored key on the bottom of the box): a. four rows of yellow balls (two rows of seven balls and two rows of six balls) b. one row of 7 red balls c. one row of six green balls d. one row of one pink ball, one white ball, one copper ball, two orange balls and two purple balls e. four rubber-banded groups of seven short wooden sticks, one rubber-banded group of nine long wooden sticks, one blue ball and one gray ball f. two rows of six black balls g. one small zip lock bag of 12 springs Have your teacher check your kit when you are done.


				
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Lingjuan Ma Lingjuan Ma
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