Final answer:
Sodium is more reactive than oxygen, especially in reactions with water, where it tend to lose its single outermost electron easily. Oxygen is also highly reactive, but its reactivity is different as it tends to gain electrons to form oxides.
Step-by-step explanation:
Between sodium and oxygen, sodium is generally more reactive. This reactivity can be attributed to the location of sodium in the periodic table; it is an alkali metal known for readily losing its single outer s electron to attain a stable electron configuration. When sodium comes into contact with water, it undergoes a violent reaction, releasing hydrogen gas and forming sodium hydroxide. This is because sodium readily loses its electron to become a positively charged ion (Na+).
Oxygen, on the other hand, is more electronegative and tends to gain electrons rather than lose them, forming oxide ions with a 2- charge. This is also indicative of its reactivity, particularly in forming oxides with metals. While oxygen is very reactive, it reacts differently than sodium. It does not exhibit the same immediacy and intensity in its reactions as sodium does with water.
Oxygen's reactivity is significant in processes like combustion and oxidation, making the chemistry of oxygen rich and well-understood.