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3 天前 · Oxygen is a chemical element; it has symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as well as with other compounds. Oxygen is the most abundant element in Earth's crust, and after hydrogen and helium, it ...
4 天前 · What links here Related changes Upload file Special pages Permanent link Page information Cite this page Get shortened URL Download QR code This chronological list of school shootings in the United States from the year 2000 includes school shootings in the United States that occurred at K–12 public and private schools, as well as at colleges and universities, and on school buses.
3 天前 · Ammonia is an inorganic chemical compound of nitrogen and hydrogen with the formula N H 3.A stable binary hydride and the simplest pnictogen hydride, ammonia is a colourless gas with a distinctive pungent smell. Biologically, it is a common nitrogenous waste, and it contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to fertilisers.
3 天前 · Silicon is a chemical element; it has symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic table: carbon is above it; and germanium, tin, lead, and flerovium are below it. It is relatively unreactive ...
1 天前 · Coal, oil, and natural gas remain the primary global energy sources even as renewables have begun rapidly increasing. Definition Renewable energy is usually understood as energy harnessed from continuously occurring natural phenomena. The International Energy Agency defines it as "energy derived from natural processes that are replenished at a faster rate than they are consumed".
3 天前 · Electronic symbol. In electrical engineering, a capacitor is a device that stores electrical energy by accumulating electric charges on two closely spaced surfaces that are insulated from each other. The capacitor was originally known as the condenser, [1] a term still encountered in a few compound names, such as the condenser microphone.
3 天前 · Venus is the second planet from the Sun. It is a terrestrial planet and is the closest in mass and size to its orbital neighbour Earth. Venus is notable for having the densest atmosphere of the terrestrial planets, composed mostly of carbon dioxide with a thick, global sulfuric acid cloud cover. At the surface it has a mean temperature of 737 ...
