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Offline Joules23

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Bond Angles Help
« on: January 05, 2008, 07:13:23 PM »
I dont see how i am getting these incorrect..
XeCl4
Elec Geometry: Octahedral
Molec shape: Square Planar
So bond angles are:
90 and 180? .. This is coming up as incorrect

ICl3
EG: Trigonal Bypyramid
MS: T-shaped
Bond angles: 90, <90, 180

TeF4
EG: Trigonal Bypyramid
MS: Seesaw
Bond angles: 90, <90, 120, <120, 180

These are the Options:
90°
< 90°
109.5°
< 109.5°
120°
< 120°
180°
< 180°

Offline Kryolith

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Re: Bond Angles Help
« Reply #1 on: January 05, 2008, 07:27:35 PM »
Bond angles are angles between three atoms. First try to figure out how many bond angles you need to determine for XeCl4, ICl3 and TeF4

EDIT
EG and MS is correct, though I don't know the meaning of seesaw, but I guess that stands for a distorted tetrahedron, doesn't it?

Offline Alpha-Omega

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Re: Bond Angles Help
« Reply #2 on: January 05, 2008, 09:17:53 PM »
Electronic Geometry:  Octahedral-Correct
Molecular Geometry:  Square Planar-Correct

The bond angles between the ligands and central atom are 90 degrees.

Bonding Pairs e-:  4

Lone Pairs of e-:  2

Hhybridization:  sp3d2


Offline Joules23

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Re: Bond Angles Help
« Reply #3 on: January 05, 2008, 09:43:32 PM »

EDIT
EG and MS is correct, though I don't know the meaning of seesaw, but I guess that stands for a distorted tetrahedron, doesn't it?

Yes, same thing

Offline Joules23

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Re: Bond Angles Help
« Reply #4 on: January 05, 2008, 09:45:00 PM »
Electronic Geometry:  Octahedral-Correct
Molecular Geometry:  Square Planar-Correct

The bond angles between the ligands and central atom are 90 degrees.

Bonding Pairs e-:  4

Lone Pairs of e-:  2

Hhybridization:  sp3d2

Thanks!... my teacher gave me a table, and it lists 90 and 180 as the angles.. but the answer that comes up correct is just 90.. Myabe the 180 is the lone-pair degree?
« Last Edit: January 17, 2012, 10:46:59 AM by Arkcon »

Offline Joules23

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Re: Bond Angles Help
« Reply #5 on: January 05, 2008, 09:50:11 PM »
For ICl3

The lone pairs would push the two outside Cl's inward toward the center Cl, right?  it would be less than 90 degrees for those.. and 180 degrees from the top

<90 & 180.. right?

Offline Alpha-Omega

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Re: Bond Angles Help
« Reply #6 on: January 05, 2008, 09:59:01 PM »
WOO HOO You are right....!!!!!!

ICl3 

Trigonal Bipyramidal-Electronic Geometry
T-Shaped-Molecular Geometry
Bonding Pairs of e-:  3
Lone Pairs of e-:   2

Hydridization:  sp3d

And you are 100% correct-bond angles 90 and 180....

GOOD JOB!!!!!!!!!!!!!!!!!!!!!!!!!  On your way to being a Quantum Chemist

Offline Joules23

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Re: Bond Angles Help
« Reply #7 on: January 05, 2008, 10:06:29 PM »
ROFL.. Thanks!!!!!!! ... btw do you have some type of software/wesbite thats telling you this.. and care to share?

Also is it 90, or <90 ?

Offline Alpha-Omega

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Re: Bond Angles Help
« Reply #8 on: January 05, 2008, 10:20:11 PM »
I am a Quantum Chemist this is my area of expertise-did my thesis on bonding using DFT...and I showed some very important results for Cobalt Tetracarbonyl complexes....

Here is a site that will help you...just the basics...but helps http://courses.ma.org/sciences/Hicks/APChemistry/APChemReadNotes/apchemreadch10.htm

Cotton and Wilkinson:  Advanced Inorganic Chemistry-he died this year was at TAMU
Shriver,Atkins, and Freeman:  Inorganic Chemistry

The TAMU site has tons and tons and tons of study and lecture notes.  All their courses are televised locally and anyone can watch them at home.  Dr. Brown started all that.  try typing in transition metal bonding TAMU  and see what you get....

And I can get you tons more...

Offline Alpha-Omega

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Re: Bond Angles Help
« Reply #9 on: January 06, 2008, 04:37:13 AM »
A molecular shape that results when there are 3 bonds and 2 lone pairs around the central atom in the molecule. The atoms bonded to the central atom lie at the ends of a "T" with 90° angles between them. ICl3 has a T-shaped molecular geometry.


VSEPR Theory

Predicts the spatial arrangement of atoms in molecules and polyatomic ions

Accounts for the geometric arrangements of electron pairs around a central atom in terms of the repulsion between electron pairs

Regions of high electron density (RHED)

The repulsion between electrons, is caused by two types of electron pairs:

                                                                                               
Bonding Electrons                                                                             

Electrons which are shared between 2 atoms                             

 

Lone Pairs 

Electrons not involved in a bond


So your angles are 90 degrees.  Due to the lone oair repulsions they are actually <90 degrees (see below and attached picture).  Taking the lone pair repusions into account the bond angled for T-Shaped AB3U2 molecule are actually 87.5 degrees.

ICL3:

AB3U2

Examples:  BrF3, ClF3, ICl3

Molecular Geometry-T-shaped
Electronic Geometry-Trigonal Bipyramidal

All molecules are polar due to lone pairs on the central atom

The See-Saw and T-Shaped geometries are both variations of the TBP (trional Bipyramidal) geometry.  The lone pairs always occupy equatorial positions. Equatorial pairs have fewer 90° repulsions, and thus are at lower potential energy.

An example of this is PCl5 wher you can see that the axial bond lengths are longer.  The greater repulsion of these lone pairs distort (bend) the both the axial and equatorial Cl atoms slightly away, to the opposite side of the molecule.

For ICl3 the T-Shape is distorted and the bond angles between the axial and equitorial ligands are 87.5 degrees so they are <90 degrees.

I have attached a picture that should help you see this.


 

 


Offline Joules23

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Re: Bond Angles Help
« Reply #10 on: January 06, 2008, 04:56:54 AM »
wow, thanks for all the info... i entered <90 and 180.. but incorrect. just <90 also incorrect.. and ran outta attempts :( .. Maybe the answer was <90 and <180 ??

What about TeF4
<90, <120 & <180 ?

Offline Alpha-Omega

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Re: Bond Angles Help
« Reply #11 on: January 06, 2008, 12:46:52 PM »
OK let s make sure we are talking about the right molecule.....do you mean the XeCl4 or do you mean the iCL3?

If it is the ICl3....you have a pic right there and all the bond angles are explained....Let me know If I have missed something or misunderstood....and this is TBP an AR3U2...The a is the central atom te I the B are the 3 bonded Cls and the U2 are the 2 unshared lone pairs....

Offline Joules23

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Re: Bond Angles Help
« Reply #12 on: January 06, 2008, 01:27:39 PM »
For the one that i got incorrect, i was talking about the ICl3
Input attempted for ICl3:
<90, 180 ..wrong
<90 .. wrong
and im assuming the correct answer was <90, <180 ?

My other question was for TeF4
are these the correct bond angles..
<90, <120 , <180 ?

Offline Kryolith

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Re: Bond Angles Help
« Reply #13 on: January 06, 2008, 01:32:14 PM »
[...]...for ICl3: im assuming the correct answer was <90, <180 ?[...]
That's correct. You have two different angles ClaxICleq < 90° and ClaxIClax < 180°

My other question was for TeF4
are these the correct bond angles..
<90, <120 , <180 ?

Are there really three angles to be determined?

Offline Joules23

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Re: Bond Angles Help
« Reply #14 on: January 06, 2008, 01:43:07 PM »
Are there really three angles to be determined?

I guess only two?... But looking at SF4, which should have the same bond angles as TeF4 (right?).. im gettin mixed signals
http://iweb.tntech.edu/chem101-tf/graphics_AX5.htm
Shows 101.4 and 86.5
http://www.uwplatt.edu/~sundin/114/plsf4.htm
shows 90 and 120
http://cnx.org/content/m12594/latest/
shows 173 and 101.5

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