I believe that the three most important elements that exist are nitrogen, carbon and oxygen. Nitrogen is extremely valuable because it is such a large part of the food web. Carbon is important because it is also part of the food web due to the fact that it plays such an important role in the structure of all living things and many nonliving things. Carbon also provides our natural fuel.
Oxygen is important because it is essential in many processes that enable life and in the transformation of energy. Oxygen can also combine with so many different elements to form numerous compounds. Nitrogen is vital in our world. About four fifths of the air we breathe is nitrogen. Most importantly, nitrogen is one of the most important elements because it is the base of the food web and it is involved in a fundamental cycle. Free nitrogen in the air is absorbed by plants and converted to plant proteins.
It is then eaten by animals that convert it to animal proteins and return it to the soil as nitrogen waste. Then bacterial action causes the nitrogen compounds to become free nitrogen again. Thus, plants need nitrogen to survive, the animals need the plant proteins to survive, and we in turn need animals and plants to survive. Without the element carbon, life as we know it would not exist. Because of its chemical characteristics, carbon is able to form many diverse organic compounds such as carbohydrates, lipids and proteins. Secondly, Carbon is important because it provides our fuels, coal, oil and natural gas.
Everyday we use things made out of carbon compounds. Some examples are sugar, starch, graphite and paper. Most importantly, carbon is found in the tissue of all plants and animals. Plants use a carbon compound called carbon dioxide (1 carbon and 2 oxygen atoms) in a process called photosynthesis. Without carbon, plants wouldn't be able to exist. Thus, carbon is also a very important part of the food web Last but not least, lets not forget oxygen.
Oxygen makes up only 20% of the air around us, but it is the reason we need to breathe. When we inhale, oxygen gets into our lungs, then it diffuses into the blood and reacts with red blood cells to produce energy. Energy is vital in every thing we do. The second reason oxygen is so important is that oxygen combines with hydrogen to make water. Without water there would be no Earth. We ourselves are made mostly of water! When we lose some of this water, we need to drink to replenish it.
Also, fish need the free oxygen that is dissolved in water and fish are a large part of the food web. Lastly, oxygen reacts with almost all of the other elements to form many compounds that are very important to us. For example, oxides. A lot of oxides are used to produce bleaches and disinfectants.
It's amazing how many organic and non-organic things can be formed and function out of just 109 elements. I believe that out of these elements, the most important ones are nitrogen, carbon and oxygen. As part of food chain, nitrogen supports all living organisms, including humans. My second choice, carbon, is also an important part of the food chain. A thing is classified organic only if it contains carbon. Carbon also provides our fuels and is used in the process of photosynthesis.
Finally, oxygen. Oxygen is part of the oxidation process, which gives energy to all living organisms. Also, oxygen is part of water, which is most abundant and one of the most important compounds on Earth. All of these three elements together with hydrogen make lipids, proteins, carbohydrates, amino acids, DNA and RNA. These are the basic building blocks of life.