Is NO2+ Polar or Nonpolar?


NO2+ is a cation known as the Nitronium ion. It contains a +1 charge by the removal of electrons from the molecule of Nitrogen dioxide that can also be achieved by protonation of nitric acid. You may have queried whether NO2+ is polar or not. In this article, I will answer this question and will also explain its properties and their applications.

So, Is NO2+ Polar or Nonpolar? NO2+ (Nitronium ion) is nonpolar in nature because it has a linear geometrical structure due to which polarity of opposite NO bonds gets canceled by each other resulting in the nonpolar NO2+ ion.

Nitronium ion is a stable ion in normal conditions. But it is also widely used as an electrophile in the nitration of various compounds.

The structure of nitronium ion is linear ie; a bond angle of 180 degrees. It is isoelectronic to nitrous acid and carbon dioxide.

Two molecules are said to be isoelectronic to each other when they have identical electronic configuration ie; same valence electrons and same geometrical structure.

Nitronium ion (NO2+) was reported first by the Raman Spectroscopy.

The systematic IUPAC name of NO2+ ion is Dioxidonitrogen(1+).

The molecular mass of Nitronium ion is calculated as

Mol mass of NO2+ = 1 * 14 (mol mass of N) + 2 * 16 (mol mass of O) = 46.005 g·mol−1.

The +1 charge on the NO2+ ion shows its high electron affinity. NO2+ cation is similar to that of NH4+ (Ammonium ion) in regards to charge.

If we talk about the charge distribution in the entire molecule, the term electronegativity is an important factor.

The electronegativity of an atom is its strength to attract the bonded electrons towards it.

In NO2+ ion, the electronegativity of oxygen is 3.44 and that of Nitrogen is 3.04. Due to this difference, the NO bond ensures some non-zero dipole moment in the direction of Oxygen.

Therefore oxygen carries a larger proportion of charge and gains partial negative charge whereas the nitrogen atom gains a positive charge.

On the other hand, the shape of the Nitronium ion is linear due to which the dipoles of NO bond are in opposite direction and gets canceled by each other resulting in the net dipole as zero.

As a result, the NO2+ ion is nonpolar in nature.

What are Polar and Nonpolar Molecules?

The bonds can be of the following types that held the molecules

  • Covalent bonds
  • Ionic bonds
  • Metallic bond
  • Hydrogen bonding

Out of the above, covalent and ionic bonds are the strongest.

In the case of the Nitronium ion, covalent bonding exists between the nitrogen and oxygen atoms.

Covalent bonds can be polar or nonpolar depending upon the various factors that are discussed briefly in below sub-topic.

Polar Molecules: The molecules are polar in nature if the atoms have unequal charge distribution on it. The two atoms form a polar covalent bond if they share bonded electron pairs unequally.

These molecules have atoms that differ in their electronegativity. Therefore, a highly electronegative atom attracts the bonded pair of electrons slightly more towards it and gains a partial negative charge.

Examples of such molecules are HBr, OF2, etc. You can also check the reason for the polarity of OF2.

Nonpolar Molecules: The molecules are said to be nonpolar if the atoms have equal charge distribution on them. Two atoms covalently bonded form a nonpolar molecule if the atoms have equal electronegativity.

As a result, they share an equal charge proportion of bonded electron pairs. Both atoms have an equal hold on bonded electrons.

Examples of such molecules are NO2+, CO2, etc.

The reason for the non-polarity of CO2 and of NO2+ is the same.

Note: It can be possible that a nonpolar molecule has polar bonds within it. But due to symmetrical shapes, the polarity gets canceled by each other. For example phosphorus pentachloride (PCl5).

Why is NO2+ a nonpolar molecule?

Nitronium ion is nonpolar in nature mainly because of its linear structure.

The Nitrogen and Oxygen atoms have unequal electronegativity ie; unequal charge distribution on both of them.

As a result, both NO bonds ensure a non-zero dipole in it, and the direction of the dipole moment is towards oxygen.

This is because the dipole is a vector quantity. It has direction as well as magnitude. The direction of dipole originates from a lesser electronegative atom to a higher electronegative atom.

But most importantly, due to the linear structure of the NO2+ ion, the dipoles of opposite NO bonds get canceled by each other.

Therefore, the nitronium ion is a nonpolar molecule.

These are factors like geometrical structure, electronegativity, and dipole that determine whether a molecule is polar or not.

For the detailed electronic structure of NO2, you must read the article on NO2 Lewis Structure, Geometry, Hybridization.

Factors affecting polarity of a molecule

If you want to check the polarity of a molecule, you just need to know the below three points about that molecule. Let us below check them what they mean actually.

Electronegativity: It is a term used to define the strength of an atom to attract the bonded pair of electrons towards it. Greater the difference between the electronegativity of two atoms covalently bonded, more is the polarity of the bond.

The polarity of a molecule is directly proportional to the difference between the electronegativity of atoms forming a molecule.

Dipole moment: It is a measure of the polarity of a molecule. Greater the dipole value of a molecule more is its polarity.
Its SI unit is Debye, denoted by D. Mathematically, it is calculated as the product of charge and the distance between them.

Geometrical Structure: The shape of the molecule determines its polarity because the symmetrically shaped molecule is nonpolar and asymmetrically shaped molecule tends to be polar.

This is because the molecules that are symmetric in shape have zero net dipole moment because in case if the molecule has non zero dipoles within it, they get canceled by each other.

Below is the image of the geometrical structure of Nitronium ion.


Properties of NO2+

  • This is a highly poisonous gas in nature. Exposure to it can lead to severe health problems including death.
    The molecular mass of Nitronium ion is 46.006 g/mol.
  • It has a high electron affinity due to a +1 charge on it. Therefore act as an electrophile in various reactions.

Uses of NO2+

  • It is widely used as an electrophile in the nitration process of other chemical compounds.
  • This cation is used to prepare different salts like nitronium perchlorate (NO+2ClO−4), nitronium tetrafluoroborate (NO+2BF−4) used for various industrial purposes.


NO2+ (Nitronium ion) is a linear-shaped molecule and an electrophile due to its high electron affinity.

In NO2+ ion, Oxygen is more electronegative than nitrogen atoms.

As a result, NO bond is polar but due to symmetric linear geometry of NO2+, the dipoles in opposite directions get canceled by each other leading to a net-zero dipole moment of the entire molecule.

Therefore, NO2+ (Nitronium ion) is nonpolar.

So guys, If you have any questions regarding the polarity of NO2+, you can ask them in the comment section. We will reach out to you as soon as possible.

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