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About 99% of the mass of the human body is made up of six elements: oxygen, carbon, hydrogen, nitrogen, calcium, and phosphorus. Only about 0.85% is composed of another five elements: potassium, sulfur, sodium, chlorine, and magnesium. All 11 are necessary for life. The remaining elements are trace elements, of which more than a dozen are ...
Standard atomic weight Ar° (As) 74.921 595 ± 0.000 006[2] 74.922 ± 0.001 (abridged) [3] view. talk. edit. Arsenic (33 As) has 32 known isotopes and at least 10 isomers. Only one of these isotopes, 75 As, is stable; as such, it is considered a monoisotopic element. The longest-lived radioisotope is 73 As with a half-life of 80 days.
Arsenic is a chemical element with the symbol As and the atomic number 33. It is a metalloid and one of the pnictogens, and therefore shares many properties with its group 15 neighbors phosphorus and antimony. Arsenic is a notoriously toxic heavy metal.
Radioactive isotopes. Radioactive isotopes are used in medicine for both treatment and diagnostic scans. The most common isotope used in diagnostic scans is Technetium-99m, used in approximately 85% of all nuclear medicine diagnostic scans worldwide. It is used for diagnoses involving a large range of body parts and diseases such as cancers and ...
This page discusses each of the main elements in the mixture of fission products produced by nuclear fission of the common nuclear fuels uranium and plutonium. The isotopes are listed by element, in order by atomic number. Neutron capture by the nuclear fuel in nuclear reactors and atomic bombs also produces actinides and transuranium elements ...
Hydrogen (1 H) has three naturally occurring isotopes: 1 H, 2 H, and 3 H. 1 H and 2 H are stable, while 3 H has a half-life of 12.32 (2) years. [3][nb 1] Heavier isotopes also exist; all are synthetic and have a half-life of less than 1 zeptosecond (10 −21 s). [4][5] Of these, 5 H is the least stable, while 7 H is the most.
Germanium occurs in five natural isotopes: 70 Ge, 72 Ge, 73 Ge, 74 Ge, and 76 Ge. Of these, 76 Ge is very slightly radioactive, decaying by double beta decay with a half-life of 1.78 × 10 21 years. 74 Ge is the most common isotope, having a natural abundance of approximately 36%. 76 Ge is the least common with a natural abundance of ...
Biological roles of the elements. A large fraction of the chemical elements that occur naturally on the Earth's surface are essential to the structure and metabolism of living things. Four of these elements (hydrogen, carbon, nitrogen, and oxygen) are essential to every living thing and collectively make up 99% of the mass of protoplasm. [1]