首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
Learn about Noble Gases(惰性气体) Have you ever ridden on a balloon? Many tourist spots offer balloon rides in order for people
Learn about Noble Gases(惰性气体) Have you ever ridden on a balloon? Many tourist spots offer balloon rides in order for people
admin
2012-12-28
94
问题
Learn about Noble Gases(惰性气体)
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 helium(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.
People once believed 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.
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 Radoa 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.
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.
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.
A. what is the periodic table?
B. What are noble gases?
C. What causes the low chemical reactivity of noble gases?
D. How were noble gases discovered?
E. How were noble gases understood in the past?
F. what are the applications of noble gases?
paragraph 3______.
选项
答案
B
解析
第三段首句是主题句,开宗明义地讲述了惰性气体是元素,有类似的属性(properties)。因此,B(什么是惰性气体)是最佳概括句。
转载请注明原文地址:https://kaotiyun.com/show/elLd777K
本试题收录于:
职称英语理工类A级题库职称英语分类
0
职称英语理工类A级
职称英语
相关试题推荐
DeforestationandDesertification(沙漠化)TheSahelzoneliesbetweentheSaharadesertandthefertilesavannahs(热带大草原)ofnort
DeforestationandDesertification(沙漠化)TheSahelzoneliesbetweentheSaharadesertandthefertilesavannahs(热带大草原)ofnort
CanAddedCalciumHelpOlderBones?NewZealandresearcherssayguidelinesadvisingseniorstoconsumeatleast1,000to1,2
MobilePhonesMobilephonesshouldcarryalabeliftheyprovedtobeadangeroussourceofradiation,accordingtoRobertBell,
ThanksgivingDayTheAmericanThanksgivingDaycelebrationgoesbackto1621.Inthatyear,aspecialdinnerwaspreparedin
Itsoundsallwrong-drillingholesinapieceofwoodtomakeitmoreresistanttoknock.Butitworksbecausetheenergyfromt
MigrantWorkersInthepast20years,therehasbeenanincreasingtendencyforworkerstomovefromonecountrytoanother.
Frommystandpoint,youknow,thisthingisjustridiculous.
A)rarelyissuccesssomysteriousB)largerewardsfollowC)IeliminatethecandidateD)weshoulddropthemandm
随机试题
2016年率先实行国家监察体制改革试点的省级地方单位是()
窦性心动过速与不适宜性窦性心动过速的鉴别要点是
女性,56岁。以反复上腹部疼痛4年为主诉来诊,上腹痛无明显规律性,伴腹胀,反酸嗳气。查体:消瘦,贫血貌,舌红无苔,上腹轻压痛。胃镜检查示黏膜红白相间,以白为主,皱襞平坦,黏膜下血管透见,黏液湖缩小。黏膜活检示重度不典型增生。当前正确的治疗方法
A.夏枯草B.密蒙花C.谷精草D.青葙子E.决明子能清肝明目,散结消肿的中药是
我国的刑事诉讼法对刑事案件的地域管辖作了具体的规定,下列哪项说法是不正确的?()
高压电抗器保护装置单体调试套用相同电压等级送配电保护装置定额。
某企业只生产一种产品,单价4.5元,单位变动成本2.7元,预计明年固定成本90000元,产销量计划达225000件。则销量对利润的敏感系数为()。
乾清宫内匾额谁写的,秘密立储制度从谁开始,诏书存放的位置?
族群是在较大的社会文化体系中,由于客观上具有共同的渊源及由此延伸出的共同的文化,因此主观上自我认同并区别于其他群体的一群人。其中共同的渊源是指世系、血统、体质的相似;共同的文化是指相似的语言、宗教、习俗等。根据上述定义,下列属于族群的一项是()。
下列定义数组的语句中正确的是()。
最新回复
(
0
)