Final answer:
Oxygen (O₂) has the highest velocity at extremely high temperatures, like those found in supernova explosions, as kinetic energy and velocity of gas particles increase with temperature.
Step-by-step explanation:
The temperature at which oxygen (O2) has the highest velocity is one where it has received the most heat energy, as kinetic energy of gas particles increases with temperature. According to the kinetic molecular theory, the root mean square (Vrms) speed of gas particles can be calculated using the equation Vrms = \( \sqrt{3kT/m} \), where k is Boltzmann's constant, T is the absolute temperature, and m is the mass of a single molecule. The kinetic energy (KE) of a gas particle is also described by the equation KE = \( \frac{1}{2}mv^2 \), indicating that as temperature increases, so does the velocity of the particles. Therefore, the velocity of O2 will be highest at extremely high temperatures, such as those found in supernova explosions, rather than at temperatures produced by stars or flames.