What is POLAR COVALENT BONDS? (1 Viewer)

[Zokunu]

I've been stuck on this for like a week or somethin right now..."Water". How do I know if a molecule is polar or not??

1) Nitrogen Trichloride (pyramidal)
2) Iodine Chloride
3) Phosphorus Tribromide (pyramidal)
4) Trichloromethane, CHCI3 (tetrahedral)

A step by step instruction would be great ....thx

PS: This is not homework....it's something that I got from a textbook..(Conquering Chemistry)

 

[someth1ng]

1) Nitrogen Trichloride (pyramidal)
2) Iodine Chloride
3) Phosphorus Tribromide (pyramidal)
4) Trichloromethane, CHCI3 (tetrahedral)

1. Spread of atoms around the central atom -> NCl3 can be modelled at a pyramid with the nitrogen atom on top. There is an uneven spread of atoms around the central atom - hence, polar.
2. Note the symmetry of the molecule -> CO2 is perfectly symmetrical about the central carbon atom (O=C=O), these causes the dipoles to cancel out and hence, non-polar.
3. Consider the differences in electronegativity of the atoms in the molecule -> ICl has iodine and chlorine atoms, both with relatively equal electronegativities (not exact but close) and hence, non-polar.

For CHCl3, the surrounding atoms are quite equally spread out causing some cancelling of dipoles (but not completely since they're different atoms) - H is a bit less electronegative than Cl. Therefore, with some cancelling of dipoles and equal spread of atoms, it is slightly polar.

 

[Zokunu]

1. Spread of atoms around the central atom -> NCl3 can be modelled at a pyramid with the nitrogen atom on top. There is an uneven spread of atoms around the central atom - hence, polar.
2. Note the symmetry of the molecule -> CO2 is perfectly symmetrical about the central carbon atom (O=C=O), these causes the dipoles to cancel out and hence, non-polar.
3. Consider the differences in electronegativity of the atoms in the molecule -> ICl has iodine and chlorine atoms, both with relatively equal electronegativities (not exact but close) and hence, non-polar.

For CHCl3, the surrounding atoms are quite equally spread out causing some cancelling of dipoles (but not completely since they're different atoms) - H is a bit less electronegative than Cl. Therefore, with some cancelling of dipoles and equal spread of atoms, it is slightly polar.

Bump...Ok thx for answering but how is NCI3 polar? Nitrogen and Chloride both have 3.0 negativety, any difference from 0.0 - 0.2 are considered "non-polar" right? This is what I think it is:

Nitrogen Trichloride

(3.0,3.0 Electronegativety) No Polar Bonds < --- Since it doesn't have polar bonds, it not's a polar molecule?

Iodine Chloride
(2.5, 3.0 Electronegativities) Polar Bond? <----Since the molecule is linear...isn't it overall a polar molecule?

Phosphorus Tribromide
(2.1, 2.8 Electronegataivities) Polar Bond? <----Uh Polar Molecule since it's pyramidal?

Trichloromethane , CHCI3

Polar Bond, Polar molecule?

Correct me if I'm wrong.....thx

 

[someth1ng]

Bump...Ok thx for answering but how is NCI3 polar? Nitrogen and Chloride both have 3.0 negativety, any difference from 0.0 - 0.2 are considered "non-polar" right? This is what I think it is:

Nitrogen Trichloride

(3.0,3.0 Electronegativety) No Polar Bonds < --- Since it doesn't have polar bonds, it not's a polar molecule?

Iodine Chloride
(2.5, 3.0 Electronegativities) Polar Bond? <----Since the molecule is linear...isn't it overall a polar molecule?

Phosphorus Tribromide
(2.1, 2.8 Electronegataivities) Polar Bond? <----Uh Polar Molecule since it's pyramidal?

Trichloromethane , CHCI3

Polar Bond, Polar molecule?

Correct me if I'm wrong.....thx

I didn't look at the values of electronegativity and that could have affected my results in my earlier response.

If the electronegativity difference is 0.5 or less, it is a non-polar bond. If it is 0.5 to 1.7, it is a polar bond and above 1.7 is usually an ionic bond.

For first case, if the electronegativities are equal, then it is non-polar (I didn't take that into consideration in the previous example).
For the second case, the electronegativities are only different by 0.5 so there's neglibible polarity and hence, the bond is non-polar.
In the last case, it will be polar since it pyramidal AND has polar bonds.

 

[Zokunu]

I didn't look at the values of electronegativity and that could have affected my results in my earlier response.

If the electronegativity difference is 0.5 or less, it is a non-polar bond. If it is 0.5 to 1.7, it is a polar bond and above 1.7 is usually an ionic bond.

For first case, if the electronegativities are equal, then it is non-polar (I didn't take that into consideration in the previous example).
For the second case, the electronegativities are only different by 0.5 so there's neglibible polarity and hence, the bond is non-polar.
In the last case, it will be polar.

So...are my answers right?

 

[someth1ng]

Nitrogen Trichloride
(3.0,3.0 Electronegativety) No Polar Bonds < --- Since it doesn't have polar bonds, it not's a polar molecule?

Iodine Chloride
(2.5, 3.0 Electronegativities) Polar Bond? <----Since the molecule is linear...isn't it overall a polar molecule?

Phosphorus Tribromide
(2.1, 2.8 Electronegataivities) Polar Bond? <----Uh Polar Molecule since it's pyramidal?

1. Don't say that it's "not polar", say that the molecule is non-polar. Otherwise, it is correct.
2. ICl has a difference of only 0.5 - usually, a difference of 0.5 or less is considered to be non-polar. Therefore, your answer is incorrect.
3. PBr3 is unevenly spread out and has a large enough difference in electronegativity (0.7). Hence, your answer is correct.

 

[Zokunu]

1. Don't say that it's "not polar", say that the molecule is non-polar. Otherwise, it is correct.
2. ICl has a difference of only 0.5 - usually, a difference of 0.5 or less is considered to be non-polar. Therefore, your answer is incorrect.
3. PBr3 is unevenly spread out and has a large enough difference in electronegativity (0.7). Hence, your answer is correct.

mhm ok thanks . What about Trichloromethane , CHCI3?

 

[someth1ng]

mhm ok thanks . What about Trichloromethane , CHCI3?

That's not the formula for trichloromethane - it's CHCl3.

Carbon has an electronegativity of 2.5.
Hydrogen has an electronegativity of 2.1.
Chlorine has an electronegativity 3.0.

If you notice, the three chlorine atoms will pull electrons slightly towards them and carbon pulls the electrons in the C-H bond towards itself. This causes higher electron density on the side of the chlorine atoms making it moderately polar.

 

[sghguos]

its pretty much HCL

 

[someth1ng]

its pretty much HCL

No, it's not.