Periodic table of the elements

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1. Periodic Table Of The Elements By: Ayah Selenium

2. Selenium is a chemical element with symbol Se and atomic number 34. It is a nonmetal with properties that are intermediate between those of its periodic table column-adjacent chalcogen elements sulfur and tellurium. It rarely occurs in its elemental state in nature, or as pure ore compounds. Selenium (Greek) Name: Selenium

3. Symbol: Se • Atomic number: 34 • Atomic weight: 78.96 (3) • Standard state: solid at 298 K •CAS Registry ID: 7782-49-2 • Group in periodic table: 16 • Group name: Chalcogen • Period in periodic table: 4 • Block in periodic table: p-block • Color: grey, metallic lustre •Classification: Non-metallic

4. Selenium has six naturally occurring isotopes, five of which are stable: 74Se, 76Se, 77Se, 78Se, and 80Se. The last three also occur as fission products, along with 79Se, which has a half-life of 327,000 years.[7][8] The final naturally occurring isotope, 82Se, has a very long.

5. This is selenium. The Color: grey, metallic luster, red, black

6. Who found it? Who found it? in nature, or as pure ore compounds. Selenium (Greek σελήνη selene s meaning "Moon") was discovered in 1817 by jons Jacob Berzelius who noted the similarity of the new element to the previously known tellurium (named for the Earth).

7. Selenium is found impurely in metal sulfide ores, where it partially replaces the sulfur. Commercially, selenium is produced as a byproduct in the refining of these ores, most often during copper production. Minerals that are pure selenide or selenate compounds are known, but are rare. The chief commercial uses for selenium today are in glassmaking and in pigments. Selenium is a semiconductor and is used in photocells . Where can it be found?

8. Selenium salts are toxic in large amounts, but trace amounts are necessary for cellular function in many organisms, including all animals. Selenium is a component of the antioxidant enzymes glutathione peroxidase and thioredoxin reductase (which indirectly reduce certain oxidized molecules in animals and some plants). It is also found in three deiodinase enzymes, which convert one thyroid hormone to another. Selenium requirements in plants differ by species, with some plants requiring relatively large amounts, and others apparently requiring none. Did You Know?

9. Medical use! The substance loosely called selenium sulfide (approximate formula SeS 2 ) is the active ingredient in some anti-dandruff shampoos.The selenium compound kills the scalp fungus Malassezia , which causes shedding of dry skin fragments. The ingredient is also used in body lotions to treat Tinea versicolor due to infection by a different species of Malassezia fungus.

10. Controversial health effects A number of correlative epidemiological studies have implicated selenium deficiency (as measured by blood levels) in a number of serious or chronic diseases, such as cancer, diabetes HIV/AIDS, and tuberculosis. In addition, selenium supplementation has been found to be a chemopreventive for some types of cancer in some types of rodents. However, in randomized, blinded, controlled prospective trials in humans, selenium supplementation has not succeeded in reducing the incidence of any disease, nor has a meta-analysis of such selenium supplementation studies detected a decrease in overall mortality