$$v=\sqrt{\frac {2K_B T}{m}}=\sqrt{\frac{2(1.38 \times 10^{23}\text{ J/K}) (273\text{ K})}{4.00\times 10^{26}\text{ kg}}}=512\text{ m/s}$$

Where,

\(K_B\) is Boltzmann's constant.

\(T\) is the temperature

\(m\) is the mass of argon