Atoms & Life
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There are 92 elements that occur naturally on Earth. For living things, only 11 of these elements are found in larger than trace quantities. Any amount 0.01 or less is considered a trace element. For vertebrates, such as humans, there are two additional elements that occur in larger than trace amounts these are Iodine and Iron.
Of the elements found in the human body, four of them make up the largest percentage of our body weight (96.2%). The four elements are oxygen, hydrogen, carbon, nitrogen. Before you start thinking we should float away with all the oxygen, hydrogen, and nitrogen atoms, remember that the oxgen molecules are mainly part of the water in our body (H2O). In fact, over half of the human body is made up of water (50-70%).