Level 5 Reading 10B

Reading 10B

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ELEMENT HUNTERS All the elements found in nature—the different kinds of atoms—were found long ago. To find a new one these days, you need to create it. Everything you know and love on Earth, and everything you don't, is built of elements—the different types of atoms. Most of them are billions of years old, scattered into space by the Big Bang or by exploding stars. They were then incorporated into the newly born Earth, endlessly recycled as they moved from rock to bacteria, president, or mouse. In the late 1800s, the Russian chemist and inventor Dmitry Mendeleyev tried to make sense of Earth's elements, grouping them by mass—the scientific term for weight— and other attributes in his periodic table of the elements. Later, scientists connected the order of elements in the periodic table to the structure of atoms. Each element got a number: its atomic number— the number of protons in its atomic nucleus. By 1940, researchers had discovered every element on Earth, right up to uranium (element 92). They had filled in every gap Mendeleyev had left in his table, but they weren't finished. Beyond uranium lay a world of possibilities—elements too radioactive and unstable to have survived billions of years. To explore that world, you have to create it first. The first steps of creation not only extended the periodic table, but played a fateful role in world history. It was 1940, the year after World War ll began, and U.S. scientists led the race to create new elements. Element 93, neptunium, was created in a laboratory at the University of California, Berkeley. The next year, Glenn Seaborg and his colleagues at the same university produced element 94, plutonium. Seaborg was promptly recruited to the Manhattan Project to create an atomic bomb for the U.S. military. The intensified level of nuclear research in the United States did not go unnoticed by the world's other superpower at the time—the Soviet Union. Georgy Flerov was a prominent physicist who had helped launch that country's nuclear weapons research. Early in World War II, Flerov had noticed that the flow of articles about radioactive elements from U.S. and German scientists had suddenly stopped. This heightened secrecy led him to suspect that they were building atomic bombs, TWENTY-SIX NEW ELEMENTS Since the 1940s, scientists have probed the frontiers of the atomic nucleus, synthesizing heavier elements one by one. The first step beyond uranium (the heaviest natural element) was neptunium, number 93 in the periodic table. The synthetic atoms are all radioactive: They decay into lighter elements, sometimes within milliseconds. In general, the heavier the element, the shorter its half-life. For decades researchers have been searching for the "island of stability," where "magic numbers" of protons and neutrons might combine to make superheavy atoms that last long enough to be studied.

元素猎手 自然界中发现的所有元素——不同种类的原子——都是很久以前发现的。 现在要找到一个新的，你需要创建它。 地球上你所知道和热爱的一切，以及你所不知道的一切， 是由不同类型的原子组成的。 它们中的大多数已有数十亿年的历史，被大爆炸或恒星爆炸分散到太空中。 然后，它们被纳入新生的地球， 当它们从岩石变成细菌、总统或老鼠时，会被无休止地回收。 19世纪末，俄罗斯化学家和发明家德米特里·门捷列夫试图理解地球的元素， 按质量分组——体重的科学术语-- 以及元素周期表中的其他属性。 后来，科学家们将元素周期表中元素的顺序与原子的结构联系起来。 每个元素都有一个数字：它的原子序数——原子核中的质子数。 到1940年，研究人员已经发现了地球上的所有元素，包括铀（元素92）。 他们填补了门捷列夫在桌子上留下的每一个空白，但还没有完成。 除了铀，还有一个充满可能性的世界——那些放射性太强、不稳定、无法存活数十亿年的元素。 要探索这个世界，你必须先创造它。 创造的第一步不仅扩展了元素周期表，而且在世界历史上发挥了决定性的作用。 那是1940年，第二次世界大战开始后的一年，美国科学家在创造新元素的竞赛中处于领先地位。 元素93镎是在加州大学伯克利分校的一个实验室中创造的。 第二年，格伦·西博格和他在同一所大学的同事们生产了元素94钚。 西博格很快被招募到曼哈顿计划，为美国军方制造原子弹。 美国核研究水平的提高 当时世界上另一个超级大国——苏联并没有忽视这一点。 格奥尔基·弗莱罗夫是一位杰出的物理学家，他帮助启动了该国的核武器研究。 在第二次世界大战初期，Flerov注意到关于放射性元素的文章流动 美国和德国科学家的研究突然停止了。 这种高度的保密使他怀疑他们正在制造原子弹， 二十六个新元素 自20世纪40年代以来，科学家们一直在探索原子核的前沿， 逐一合成较重的元素。 铀（最重的天然元素）之外的第一步是镎，在元素周期表中排名第93位。 合成原子都是放射性的： 它们会衰变成较轻的元素，有时在几毫秒内。 一般来说，元素越重，半衰期越短。 几十年来，研究人员一直在寻找“稳定岛” 在那里，质子和中子的“神奇数字”可能会结合在一起，形成能够持续足够长时间进行研究的超重原子。

and in April 1942, he wrote to Soviet leader Joseph Stalin explaining his fears. Flerovs suspicions were confirmed, and Stalin asked Russian physicists to build a bomb, too. For his part in the war effort, Flerov was rewarded with a car, a house, and, most significantly, a laboratory in the town of Dubna, north of Moscow. There, Flerov focused his attention on the hunt for new elements. His American counterpart, Glenn Seaborg, returned to Berkeley after helping to engineer the bomb that the U.S. military dropped on Nagasaki at the end of the war. He continued to make new elements, with less fateful applications— smoke detectors, for instance—or no applications at all. By 1955, his team had gotten as far as element 101—he named it mendelevium. For a time it seemed Mendeleyev's table might end there, with his namesake. The protons in an atomic nucleus are always trying to tear it apart; their positive electric charges repel one another. Neutrons—electrically neutral particles that out number the protons—help bind the nucleus together. But that binding force works only at extremely close range, and it weakens sharply as the size of the nucleus increases. So there has to be a final box on the periodic table, a maximum size beyond which an atom won't be stable even for an instant. With mendelevium, which has a half-life of 51.5 days, researchers seemed to be getting close to the final box. Beyond Mendelevium The Berkeley team continued its research regardless, rivaled by Flerovs team in Dubna. From 1965 to 1974, Berkeley claimed to have produced elements 102-106—but so did the Dubna lab. Although those short-lived elements died within hours, the tense disputes over who made them first were fueled by the competitive atmosphere of the Cold War. In the end, a spirit of compromise prevailed: Element 105 was named dubnium and element 106 seaborgium. Meanwhile, theorists had given a new purpose to the quest for elements. They calculated that a very large nucleus might be surprisingly stable if it had "magic numbers" of protons and neutrons. That insight, if correct, would change everything. It would mean that there could be an "island of stability" where extremely heavy elements might last minutes, weeks, or even thousands of years. Around the time that this new theory appeared, a brilliant physicist named Yuri Oganessian joined Flerov's lab in Dubna. The island of stability had captured his imagination. However, reaching it seemed to him an impossible task at that point. The Berkeley and Dubna labs had gotten only as far as element 106 by shooting light atoms against heavy ones with such force that they joined to create a single superheavy nucleus. But beyond 106, the collisions were so energetic that they were ripping the new nucleus apart before it even formed. To overcome this problem, Oganessian proposed that shooting slightly heavier atoms at lighter targets might create gentler collisions that were more likely to create new elements. Unfortunately, before he could put his proposal into action, a lab in Darmstadt, Germany, used the idea to make elements 107 through 112. Oganessian's historic moment would have to wait another quarter century. In the coming years, the Dubna lab went through hard times. Flerov died in 1990; the Soviet Union collapsed in 1991. The lab went months without being able to pay its researchers. Scientists gathered mushrooms in the forests and fished in the Volga River. Oganessian, now in charge of the lab, could have directed it toward more practical goals and made some money for himself and his staff, but he decided instead to continue toward element 114 and the promised island of stability. Achieving the Dream To make element 114, Oganessian would shoot calcium at plutonium. He persuaded U.S. physicists at the Lawrence Livermore National Laboratory in California— who just a few years earlier had been his rivals—to give him a small amount of plutonium. The plan was to use a cyclotron to shoot a beam of calcium atoms at high speed into a thin sheet of metal covered with the precious plutonium atoms. Among the trillions of atoms spraying out the other side— the metal sheet was thinner than hair—Oganessian expected at most one atom of element 114. His team—along with Livermore's—invented a new device to detect it. They turned the cyclotron on in November 1998. It wasn't a very trust worthy piece of machinery, and it required constant attention. Nevertheless, in late November, the cyclotron managed to produce a single atom of element 114. It lasted only a few seconds— but that was thousands of times longer than would be expected if there were no island of stability. It also proved that the calcium method worked. Dubna and other labs have since made elements 115-118, and isotopes with different numbers of neutrons. They are still nowhere near the island's peak, where an element might last years, but the creation of element 114 was the great breakthrough that Oganessian had been dreaming about for decades. It wasn't until 2011, however, that element 114 was officially admitted to the periodic table. This is because no newly discovered element is officially recognized until another laboratory can duplicate the experiment, which sometimes takes years. Element 114 was given the name flerovium. This belated but welcome recognition came when Oganessian was 78 years old. After such a triumph, other scientists might have decided it was time to retire to a quiet and grateful life— but not Yuri Oganessian. The island of stability still captures his imagination, inspiring him on to further discoveries. As Oganessian put it, "We have discovered the island. Now it is time to explore it, to walk along its western beach." Techniques must be developed to shoot the magic number of neutrons into flerovium to reach its peak of stability. Scientists need to discover if there are peaks at other elements. Although at the moment those goals seem almost impossible, Oganessian has no intention of giving up the hunt for new elements.

1942年4月，他写信给苏联领导人约瑟夫·斯大林，解释了他的担忧。 Flerovs的怀疑得到了证实，斯大林也要求俄罗斯物理学家制造炸弹。 由于他在战争中的贡献，Flerov获得了一辆汽车和一栋房子作为奖励， 最重要的是，位于莫斯科北部杜布纳镇的一个实验室。 在那里，Flerov将注意力集中在寻找新元素上。 他的美国同行格伦·西博格， 在协助设计炸弹后返回伯克利 美国军队在战争结束时投放在长崎。 他继续创造新的元素，但不那么具有决定性的应用-- 例如烟雾探测器——或者根本没有应用。 到1955年，他的团队已经找到了101号元素，他将其命名为mendelevium。 有一段时间，门捷列夫的桌子似乎就在这里结束了，以他的名字命名。 原子核中的质子总是试图将其撕裂； 它们的正电荷相互排斥。 中子——数量超过质子的电中性粒子——有助于将原子核结合在一起。 但这种约束力只在极近的距离内起作用， 随着细胞核大小的增加，它急剧减弱。 所以元素周期表上必须有一个最后的方框， 一个最大尺寸，超过这个尺寸，原子即使在一瞬间也不会稳定。 对于半衰期为51.5天的孟替利， 研究人员似乎正在接近最后一个盒子。 超越孟德尔 伯克利团队继续进行研究，与杜布纳的Flerovs团队竞争。 从1965年到1974年，伯克利声称已经生产了102-106号元素，但杜布纳实验室也是如此。 尽管这些短寿命的元素在数小时内死亡， 冷战的竞争氛围加剧了关于谁先制造这些武器的紧张争端。 最终，妥协的精神占了上风： 元素105被命名为dubnium，元素106被命名为seaborgium。 与此同时，理论家们为寻找元素赋予了新的目的。 他们计算出，一个非常大的原子核可能出乎意料地稳定 如果它有质子和中子的“神奇数字”。 这种见解，如果正确的话，将改变一切。 这意味着可能会出现一个“稳定岛” 极重元素可能持续数分钟、数周甚至数千年。 在这个新理论出现的时候， 一位名叫Yuri Oganessian的杰出物理学家加入了Flerov在杜布纳的实验室。 稳定之岛激发了他的想象力。 然而，在他看来，在那一点上，实现这一目标似乎是一项不可能的任务。 伯克利和杜布纳实验室只研究了106号元素 用这种力量把轻原子射向重原子 它们结合在一起形成了一个超重的原子核。 但在106年以后，碰撞的能量是如此之高 他们甚至在新细胞核形成之前就把它撕裂了。 为了克服这个问题，Oganessian提出向较轻的目标发射稍重的原子 可能会产生更温和的碰撞，更有可能产生新元素。 不幸的是，在他将他的提议付诸行动之前， 德国达姆施塔特的一个实验室利用这一想法制造了107至112号元素。 Oganessian的历史性时刻将不得不再等25年。 在接下来的几年里，杜布纳实验室经历了艰难的时期。 Flerov于1990年去世；1991年苏联解体。 该实验室几个月来一直无法支付研究人员的工资。 科学家们在森林里采集蘑菇，在伏尔加河捕鱼。 Oganessian现在负责实验室， 本可以将其导向更实际的目标，并为自己和员工赚些钱， 但他决定继续朝着114号元素和承诺的稳定岛前进。 实现梦想 为了制造元素114，Oganessian会向钚发射钙。 他说服了加利福尼亚州劳伦斯利弗莫尔国家实验室的美国物理学家-- 就在几年前，他还是他的竞争对手——给他少量的钚。 计划是用回旋加速器发射一束钙原子 以高速进入覆盖有贵钚原子的薄金属片。 在从另一边喷出的数万亿个原子中-- 金属片比头发还薄——Oganessian预计最多只有一个元素114原子。 他的团队与利弗莫尔的团队一起发明了一种新的设备来检测它。 他们在1998年11月打开了回旋加速器。 这不是一台值得信赖的机器，需要不断的关注。 然而，在11月下旬，回旋加速器设法产生了一个元素114的原子。 它只持续了几秒钟-- 但如果没有稳定岛，这比预期的要长数千倍。 这也证明了钙法是有效的。 杜布纳和其他实验室已经制造了元件115-118， 以及中子数不同的同位素。 它们还远未达到岛屿的顶峰，那里的元素可能会持续数年， 但114号元素的创造是奥加涅西安几十年来一直梦想的重大突破。 然而，直到2011年，元素114才被正式纳入元素周期表。 这是因为没有新发现的元素得到官方认可 直到另一个实验室可以复制这个实验，这有时需要数年时间。 元素114被命名为flerovium。 当Oganessian 78岁时，这一迟到但受欢迎的认可出现了。 在取得这样的胜利之后，其他科学家可能会决定是时候退休，过上平静而感激的生活了-- 但尤里·奥加涅相却不是。 稳定之岛仍然吸引着他的想象力，激励他进一步探索。 正如Oganessian所说，“我们发现了这座岛。 现在是时候去探索它了，沿着它的西部海滩散步。" 必须开发技术，将神奇数量的中子射入氟罗威姆，以达到其稳定的峰值。 科学家们需要发现其他元素是否存在峰值。 尽管目前这些目标似乎几乎不可能实现， Oganessian无意放弃寻找新元素。

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