In drawing the Lewis structure for C2H2 (also called ethyne) you'll find that you don't have enough valence electrons available to satisfy the octet for each element (if you use only single bonds). The solution is to share three pairs of valence electrons and form a triple bond between the Carbon atoms in C2H2
Atoms become unstable when the neutrons and protons are off-balance. Neutrons serve as a type of atomic “glue” that holds the nucleus together. Throw that ratio off balance, and the whole atom goes kaput.
Answer:
Equilibrium will be shifted towards NO2 as it has the most of the moles in the reaction.
Explanation:
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In this case, according to the equilibrium reaction between NO2 and N2O4, we are able to write:

We can recall the LeCha-telier's principle to realize that the increase of volume promotes the formation of the most of the moles, this is for NO2 because it has a coefficient of 2 and N2O4 a coefficient of 1; in such a way, we infer that the addition of argon, to increase the pressure, will shift the equilibrium towards NO2.
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