NO2+ is a nonpolar molecule despite two N-O bonds are polar. NO2+ has a linear geometry due to no lone pair of electrons on central N atom which causes cancellation of both positive and negative charges produced on the molecule, as a result, the net dipole becomes zero.
Detailed Explanation: Why is NO2+ a Polar molecule?
NO2+ is Nitrogen Dioxide Cation known as Nitronium ion.
Nitronium ion is created by the removal of an electron from a paramagnetic nitrogen
dioxide molecule. It can also be produced by the removal of H2O from Nitric acid
which is called protonation of Nitric acid. (not to be confused with Nitrite ion
which is NO2-).
Before entering into its polarity behavior first, have some
basic ideas about polar and nonpolar molecules,
Polar Molecules
Polar molecules are those molecules having polar bonds
within the molecule and have irregular geometry (Not linear or symmetrical) so
that the dipole charges (partial positive and negative) on the molecule don't cancel out. For a molecule to be polar, there must be some net dipole moment and
this can’t be zero otherwise the molecule becomes nonpolar.
Molecules having polar covalent bonds show both ionic and
covalent characteristics. They can easily be soluble in water, can conduct
electricity and many more ionic behaviors.
Examples of Polar molecules: Water (H2O), Ammonia (NH3), Hydrogen bromide (HBr), etc.
Nonpolar Molecules
Polar molecules are those molecules having a net dipole moment
zero i.e. electronegativity of the atoms in a molecule must be the same or have
regular geometry (symmetrical or linear). Nonpolar molecules are considered as
pure covalent bonds because they only show covalent nature unlike nonpolar
molecules that also show little ionic behavior.
Nonpolar molecules are not soluble in water or any other
polar solvents. These are only soluble in nonpolar solvents and also they are bad
conductors of heat and electricity as they don’t have free ions.
Example of Nonpolar molecules: Carbon Dioxide (CO2), Methane
(CH4), Diatomic molecules etc.
Nitronium Ion (NO2+) Polar or Nonpolar (Based on characteristics)
NO2+ is a Nonpolar molecule and the Oxygen atom closest to
negative side as the electronegativity value of Oxygen (3.44) is higher than
Nitrogen (3.04) so that Oxygen atoms slightly attract the electron from Nitrogen
atom which results in partial positive charge on the Nitrogen atom and negative
charge on Oxygen atoms but canceled out due to the linear structure of the
molecule.
These are some of the characteristics of NO2+ to elaborate
why it is a nonpolar molecule:
Electronegativity Difference
Electronegativity is the tendency of an atom to attract
electrons from other atoms within the molecule. A higher E.N value indicates an atom
has a higher tendency to attract electrons from its corresponding binding partner
atom.
In Nitronium ion, Oxygen atoms (3.44) have higher E.N than
Nitrogen atom (3.04) so that two N-O bonds are polar in nature. But polarity of
the molecule is finalized after considering the entire molecule whether dipole
charges are canceled out or not.
Learn More: Why is NO2 is a polar molecule whereas NO2+ is nonpolar?
Lewis Structure & Molecular Geometry
In NO2+, a total of 16 valence electrons participate in
molecule formation because +1 indicates Nitrogen atom has one less valence
electron. This is the main reason why NO2+ has linear geometry as there is not
any lone pair of electrons present in the central nitrogen atom.
Due to no unbonded lone pair of electrons on the N atom, no
electron-electron repulsion exerts within the molecule which results in the bond
angle is idle 180. Thus, bond polarity is canceled by each other and resulting
in net dipole moment zero.
Dipole Moment
The dipole moment is the product of charge and distance between
the atoms. In NO2+, two N-O bonds have partial positive and negative charges
established due to differences in E.N but the dipole moment is a vector quantity so
the results of the charges are considered as net dipole moment. Here, both
N-O bonds polarity canceled out due to the linear structure of the molecule as
mentioned above. This results in the net dipole moment zero so the molecule is also
Nonpolar.
Solubility Principle
According to the solubility principle “like dissolves like”, NO2+ the molecule is only soluble in nonpolar solvents like Carbon tetrachloride (CCl4),
Benzene (C6H6), Methylene Chloride (CH2Cl2), etc, and insoluble in polar
solvents like water (H2O), Ethanol (C2H5OH), etc.
Sources of Nitronium ion (NO2+)
The major sources of NO2+ are the combustion of fossil fuels like
diesel, petrol, coal, and different gases. In general lab preparation, its major
source of preparation is through protonation of nitric acid i.e. removal of the water
molecule in the presence of sulfuric acid.
Properties of Nitronium ion (NO2+)
1. NO2+ has a molecular mass of 46.005 g.mol-1 and a bond angle of 180.
2. It is only soluble in nonpolar solvents (benzene, carbon
tetrachloride, etc) and insoluble in polar solvents (water, ammonia, etc).
3. It is a toxic gas, poisonous in nature which causes
Pulmonary edema and many severe lung problems in living organisms.
4. It has a high electron affinity due to the presence of +1 charges
on the nitrogen atom so it acts as an electrophile in titration.
Uses of Nitronium ion (NO2+)
- Mostly used as an electrophile in the nitration.
- Uses in preparation of different commercial salts like Nitryl fluoride (NO2F) and Nitryl chloride (NO2Cl).
- It is also used in the preparation of fertilizers and related products.
Post a Comment