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Anonymous users2024-02-07Discovered in 1899.
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Anonymous users2024-02-061. Polonium (Polonium, PO) is a silvery-white metal, which can glow in the dark, discovered in 1898 by Marie Curie and her husband Pierre Curie. Polonium is one of the rarest elements known, with a content of about 100 parts per trillion in the earth's crust, and polonium is mainly obtained by artificial synthesis. Polonium is one of the most toxic substances in the world.
2. Because 1 gram of polonium-210 can cause the death of 10 million people out of 20 million people (that is, the semi-lethal dose of 20 million people is 1 gram, and the semi-lethal dose next to one person is 1 gram of 20 million), so polonium is the most toxic substance.
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Anonymous users2024-02-05From the calculation methods of the two division formulas of 400 4 and 440 4, it can be seen that a multi-digit number (with a few zeros at the end) is divided by a single digit, and when it is divided by a certain digit, there are several zeros after this digit, and the same number of zeros must be added at the end of the quotient.
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Anonymous users2024-02-049 44 and 9 444 can be found to be a multi-digit number composed of n 9 multi-digit numbers multiplied by n 4s, and the product has a multi-digit number composed of (n-1) 4, a 3, (n-1) 5 and a 6. According to the query related to the disclosure of which celebration information is displayed, so the solution: 9 4 = 36,99 44 = 4356,999 444 = 443556, this question examines the law in arithmetic, carefully calculates, analyzes, and finds the law is the key to solving this problem.
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Anonymous users2024-02-03A metallic element, silvery-white, soft, soluble in acids. Generally, it oxidizes rapidly in the air and loses its luster. It is mainly found in the extremely rare scandium yttrium. It can be used to make special glass and lightweight high-temperature resistant alloys.
Scandium is used to make special glass, lightweight high-temperature resistant alloys.
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Anonymous users2024-02-02In 1879, Swedish chemistry professors Nelson (1840-1899) and Clive (1840-1905) found a new element in the rare minerals silicon-beryllium yttriumite and black rare gold ore at about the same time. They named the element scandium, which was the boron-like element that Mendeleev had predicted. Their findings once again proved the correctness of the periodic law and Mendeleev's foresight.
Robert Hooke, is a ground glass. He grinded the glass into a lens and discovered the cell!
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In the new textbook, based on the unanimously recognized research results of the archaeological community, we have made the following statement about the earliest known human beings in China: "Yuanmou Man lived about 1.7 million years ago, and it is the earliest known human in China. "However, since the 80s and 90s of the 20th century, there have been more advances and new discoveries in archaeology as to whether there were earlier human activities in our country. >>>More