[1] Diatomics may refer to the study of elements that have only two molecules. Such molecules are ka diatomic. And they're characteristic of Earth's most common elements: carbon, hydrogen, nitrogen, and oxygen. [2] Diatomics may also refer to the study of diatoms. Diatoms are algal organisms that have a nucleus. The nucleus is the location of the organism's genetic material. Diatoms process 1/4 of the world's carbon, and 1/5 of oxygen. They may be found in fresh and salt water, and soil.