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A space-filling model of the diatomic molecule dinitrogen, N 2. Diatomic molecules (from Greek di- 'two') are molecules composed of only two atoms, of the same or different chemical elements. If a diatomic molecule consists of two atoms of the same element, such as hydrogen (H 2) or oxygen (O 2), then it is said to be homonuclear.
Some compounds may be carcinogenic; some forms are mildly toxic to humans. [11] selenium: 34: 4: Selenium, which is an essential element for animals and prokaryotes and is a beneficial element for many plants, is the least-common of all the elements essential to life.
Parts-per-million cube of relative abundance by mass of elements in an average adult human down to 1 ppm. By mass, human cells consist of 65–90% water (H 2 O), and a significant portion of the remainder is composed of carbon-containing organic molecules. Oxygen therefore contributes a majority of a human body's mass, followed by carbon.
Two or more atoms can combine to form molecules. Some elements are formed from molecules of identical atoms, e. g. atoms of hydrogen (H) form diatomic molecules (H 2). Chemical compounds are substances made of atoms of different elements; they can have molecular or non-molecular structure.
Some of the largest molecules are macromolecules or supermolecules. The smallest molecule is the diatomic hydrogen (H 2), with a bond length of 0.74 Å. [24] Effective molecular radius is the size a molecule displays in solution. [25] [26] The table of permselectivity for different substances contains examples.
In chemistry and biology, reactive oxygen species (ROS) are highly reactive chemicals formed from diatomic oxygen (O 2), water, and hydrogen peroxide. Some prominent ROS are hydroperoxide (O 2 H), superoxide (O 2 −), [1] hydroxyl radical (OH.), and singlet oxygen. [2] ROS are pervasive because they are readily produced from O 2, which is ...
Pie charts of typical human body composition by percent of mass, and by percent of atomic composition (atomic percent) Body composition may be analyzed in various ways. This can be done in terms of the chemical elements present, or by molecular structure e.g., water , protein , fats (or lipids ), hydroxyapatite (in bones), carbohydrates (such ...
Other important organic compounds that contain oxygen are: glycerol, formaldehyde, glutaraldehyde, citric acid, acetic anhydride, and acetamide. Epoxides are ethers in which the oxygen atom is part of a ring of three atoms. The element is similarly found in almost all biomolecules that are important to (or generated by) life.