理工 B21 概括大意与完成句子

花开自在

Learn about Noble Gases（惰性气体）　　1 Have you ever ridden on a balloon? Many tourist spots offer balloon rides in order for people to see the beauty of a place from above. A balloon contains a noble gas called hellum（氦）. Formerly, balloons contained hydrogen but hydrogen is very flammable and dangerous when uncontrolled. Therefore, people shifted to helium, which is safer. Helium is safe because it has the properties of the noble gases.
　　 2 People once belleved that noble gases couldn’t chemically react at all. For this reason, they were called inert gases（惰性气体）. They were also listed under Group 0 in the old periodic table because scientists believed that the gases have zero valence（价）electrons in their outer shell. This was later proven to be untrue when some noble gas compounds were discovered.
　　 3 The gases are elements, which share similar properties. These properties include being monoatomic, colorless, odorless, being able to conduct electricity, and having low chemical reactivity. Noble gases include Helium, Neon, Argon, Krypton, Xenon and Radon. These are all found in Group 18, in the rightmost column of the periodic table. If you look at the periodic table, you will notice that these elements are the only ones, which do not have a charge. Helium has the lowest molecular（分子的）weight while Radon is the heaviest.
　　 4 Remember that chemical reactions occur because atoms have valence electrons, which are electrons in their outer shell. When the outer shell is “unfilled” or the required number of electrons is not yet complete, the atom is more reactive. Noble gases have a full outer shell, meaning that they have complete electrons in their outer shell. This complete number varies. For instance, the outer shell of Helium has 2 valence electrons while the outer shell of Xenon has 8 electrons. Nowadays, there remains to be a few noble gases because of the low chemical reactivity of these said gases.
　　 5 because of their properties, noble gases have many important applications. They are widely used in medicine and industries. For instance, liquid Helium is used for superconducting magnets（磁体）. These magnets are very important in physics and medicine. When a doctor suspects that a person’s brain has been damaged, he might request for Magnetic Resonance Imaging(MRI). MRI allows the doctor to “see” the brain, without operating on the patient.
　　 23. paragraph 2______D__
第2段主要讲解人类过去的惰性气体的认识
　　 24. paragraph 3__F______
什么是惰性气体
　　 25. paragraph 4_____E___
惰性气体为何不易发生反应
　　 26. paragraph 5_______C_
惰性气体的应用
　　 A. How were noble gases discovered?
　　 B. what is the periodic table?
　　 C. what are the applications of noble gases?
　　 D. How were noble gases understood in the past?
　　 E.What causes the low chemical reactivity of noble gases?
　　 F. What are noble gases?
　　 27. Noble gases are not very chemically . 答案B 惰性气体不易发生化学反应
　　 28. Among the elements of noble gases Helium is the .答案 F 氦气是惰性气体中最轻的
　　 29. The required number of electrons in noble gases’outer shell is . 惰性气体的外层需要的电子数，我选择的是C unnecessary
　　 30. MRI may make operating on the patient . 答案选E，应是重要的
　　 A. complete
　　 B. reactive
　　 C.unnecessary
　　 D. flammable
　　 E. important
　　 F. lightest

【向日葵微笑】

我有2个选项和你不一样，
29. The required number of electrons in noble gases’outer shell is . A. complete 参考： the required number of electrons is not yet complete, the atom is more reactive. Noble gases have a full outer shell, meaning that they have complete electrons in their outer shell.
30. MRI may make operating on the patient C.unnecessary 参考：MRI allows the doctor to “see” the brain, without operating on the patient.

无知大儿

同意2楼的答案

0°dê冰

二楼答案是对的。