First of all we need to define polar and non polar:

Polar molecules:

Polar molecules have to grab polar bonds due to a difference in electronegativity among the bonded atoms. A molecule will be polar if it have two or more polar bonds produced an asymmetric geometry so that the bond dipoles do not cancel each other effects.

Here are some examples of polar molecules:

Ammonia (NH3), Sulfur Dioxide (SO2) and Hydrogen Sulfide (H2S) etc.

Nonpolar molecules:

A nonpolar molecule either formed due to an equal sharing of electrons among the two atoms of a diatomic molecule or due to the symmetrical array of polar bonds in mainly complex molecules. Here are some examples of polar molecules:

Nitrogen (N2), Oxygen (O2), Carbon Dioxide (CO2), Methane (CH4), Ethylene (C2H4) etc.

Is NO2+ Polar or Nonpolar?

 NO2+ is a nonpolar molecule due to its linear structure which cancels out opposite dipole forces. On result of this a molecule  formed that does not have permanent partial charges.

NO2+ is called as Nitronium ion not to be baffled with the nitrite ion (or NO2-) which does not have a linear structure. NO2+  is a cation comparable to ammonium (NH4+) in consider to its charge. 2+ means that molecule has lost their 2 electrons to get stable. While NO2+ can be formed and after that exist stably in normal conditions, it is fairly reactive on its own merit.

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