A mixture of N2O4(g) and NO2(g) is at equilibrium at 298 K in a sealed, rigid container. An additional 1.0 atm of argon is injected, raising the total pressure. Explain whether the numerical value of Kp for the reaction
N2O4(g) ⇌ 2 NO2(g)
changes, and justify your answer in one or two sentences.