Answer:
O₂
Step-by-step explanation:
Oxygen makes up about 21% of the atmosphere. It's a very reactive chemical element and can combine with almost anything to make various compounds. Fire, for example, so useful for heat and light yet so damaging to wood structures, is a vigorous reaction of oxygen with burnable materials like wood or other fuels. Many metals react with oxygen to form oxides. Of particular commercial interest is the collection of iron oxides known as rust. A billion dollar problem around the world, rust weakens bridges and buildings, damages engines and tools, and corrodes pipes.
Yet oxygen is also essential for living things. Oxygen releases energy from nutrients in every living cell, a process called cellular respiration. One type of oxygen, ozone, protects us from the most damaging ultraviolet light in sunlight. You might be wondering why such a reactive element is still present in the atmosphere in such large quantities after all this time. The answer is photosynthesis, carried out by all green plants. Oxygen is a waste product of photosynthesis, which fuses water and carbon dioxide into sugars, so you can think of your local park or forest as a place where oxygen is pumped back into the environment.
Oxygen is a element in the periodic table