Why is NO3 nonpolar but CIF3 is polar? I looked at the lewis structures, they look similar, but why is one opposite.
also, when something is polar or non polar, my teacher said I should see which atom is more electronegativity is higher and draw arrows towards it on a lewis structure, then add "vectors"
What does that mean? can you explain the question above with vectors. I tried doing it and the vectors don't cancel for both of them, but apparently it does cancel for NO3.
1. The NO3^- ion (I assume you just omitted the negative charge) is a trigonal planar molecule; therefore, the polar bonds between individual N and O cancel for the molecule due to the shape of the molecule; i.e., the molecule is symmetrical. The NO3^- is what we call an AB3 type molecule and that leads to it being trigonal planar. This site shows the structure but scroll through to the very bottom.
http://www.molecularsoft.com/help/Chemical_Bonds-Lewis_Structure.htm The ClF3 molecule, however, is an AB3U2 type molecule with two unpaired sets of electrons and a geometry of trigonal bipyramidal. Here is a site that shows that.
http://www.up.ac.za/academic/chem/mol_geom/t.htm
Here the atoms also have individual polarity but the molecular symmetry does not cancel the polarity of the molecule.
To determine whether a molecule is polar or nonpolar, you can use the concept of electronegativity and the Lewis structure.
In the case of NO3 (nitrate), let's draw its Lewis structure:
N = O(1) - O(2) - O(3)
The electronegativity of nitrogen (N) is relatively high compared to oxygen (O). Since the O atoms are more electronegative, they will draw electron density towards themselves, creating a partial negative charge (-) on the oxygen atoms and a partial positive charge (+) on the nitrogen atom. However, these charges are evenly distributed around the nitrogen atom, resulting in a symmetrical molecular geometry. Because of this symmetry, the bond polarities cancel each other out, making NO3 a nonpolar molecule.
On the other hand, let's examine CIF3 (chlorine trifluoride):
Cl - F1
|
F2
The electronegativity of chlorine is higher than that of fluorine. Therefore, the chlorine atom in CIF3 has a higher electron density, creating a partial negative charge (-). The fluorine atoms have a partial positive charge (+) due to their lower electronegativity. These charges are not evenly distributed around the molecule, resulting in an asymmetrical molecular geometry, which makes CIF3 a polar molecule.
Now, let's talk about the concept of vectors. In the context of molecular polarity, vectors represent the direction and magnitude of the partial charges within a molecule. To determine the overall molecular polarity, you need to consider the vector sum of the individual bond polarities.
For NO3, the three O-N bonds have the same bond polarities. Since the molecule is symmetrical and the vectors point in opposite directions (towards the oxygen atoms), their magnitudes cancel each other out, resulting in a net dipole moment of zero. Hence, NO3 is nonpolar.
For CIF3, the vectors do not cancel each other out. The bond polarities result in a net dipole moment, making CIF3 a polar molecule.
In summary, the polarity of a molecule is determined by the distribution of partial charges and the geometry of the molecule. It is important to consider both the electronegativity differences between atoms and the molecular geometry when determining whether a molecule is polar or nonpolar.
The polarity of a molecule is determined by the difference in electronegativity between its constituent atoms and the molecular geometry. Let's first take a look at the Lewis structures of NO3- and CIF3 to understand their polarity.
NO3-:
- The Lewis structure of NO3- consists of a central nitrogen atom bonded to three oxygen atoms. Nitrogen is more electronegative than oxygen, so the arrows representing the electron distribution will point towards the nitrogen atom. The three oxygen atoms create a trigonal planar molecular geometry around the nitrogen atom, with a lone pair of electrons on the nitrogen atom.
- The arrows represent the movement of electrons from the less electronegative atom (oxygen) towards the more electronegative atom (nitrogen). The resultant vectors do not cancel each other out completely, resulting in a net dipole moment. Hence, NO3- is a polar molecule.
ClF3:
- The Lewis structure of ClF3 consists of a central chlorine atom bonded to three fluorine atoms. Chlorine is less electronegative than fluorine, so the arrows representing the electron distribution will point towards the fluorine atoms. The three fluorine atoms create a T-shaped molecular geometry around the chlorine atom, with two lone pairs of electrons on the chlorine atom.
- Again, the arrows represent the movement of electrons from the less electronegative atom (chlorine) towards the more electronegative atom (fluorine). However, in this case, the resultant vectors do not cancel each other out, resulting in a net dipole moment. Hence, ClF3 is a polar molecule.
The concept of vectors is used to calculate the resultant dipole moment of a molecule. Each bond represents a dipole moment, which has both magnitude and direction. The direction is determined by the electronegativity difference between the bonded atoms. When multiple bond dipoles are present in a molecule, their vector sum is calculated to determine the net dipole moment of the molecule. If the vector sum is zero, the molecule is nonpolar. If the vector sum is nonzero, the molecule is polar.
In the case of NO3-, the three bond dipoles are in a trigonal planar arrangement, with equal magnitudes but different directions. The vector sum of these bond dipoles is zero, resulting in a nonpolar molecule. However, in the case of ClF3, the three bond dipoles are in a T-shaped arrangement, with equal magnitudes but different directions. The vector sum of these bond dipoles is nonzero, resulting in a polar molecule.
It's important to note that the presence of a net dipole moment and molecular geometry both contribute to the polarity of a molecule. Simply looking at the electronegativity difference and drawing arrows can provide a rough idea, but using vectors allows for a more accurate determination of a molecule's polarity.