Which of the following was the most active element in the primitive atmosphere on earth ?

Step-by-step solution

The primitive atmosphere of the earth was highly reducing in nature. Hydrogen was the most abundant and most active element in the primitive atmosphere. It readily reacted with other elements such as oxygen, nitrogen, and carbon to form water, ammonia, and methane, respectively. Because of its high reactivity and abundance, free oxygen was not present, making the atmosphere reducing. Answer: Hydrogen