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
95
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
LivingAloneCouldBeGoodforYourWeightGoodnewsforpeoplelivingalone:Aforthcomingpapershowsthatsingleadults—o
DuringtheApril28earthquake,thewholeEnglandwasleftwithoutpower.FranceandseveralotherEuropeancountriessentthei
AvalancheandItsSafetyAnavalancheisasuddenandrapidflowofsnow,oftenmixedwithairandwater,downamountainside.A
HowtheBodyKeepstheSameTemperatureThetemperatureofyourbodyshouldbealwaysjustthesame,nomatterwhethertheweath
AnIntelligentCarDrivingneedssharpeyes,keenears,quickbrain,andcoordinationbetweenhandsandthebrain.Manyhumandr
ALEDLightingIsNotMatureBLEDLightingWillReplaceTraditionalLightingCAlmostEverythingCouldBetheMainLight
EnergyCycleDoyoufindgettingupinthemorningsodifficultthatit’spainful?Thismightbecalledlaziness,butDr.Kl
ContinuetoProtectorDestroyEcosystemBiosphereIIwasaspectacularfailure.Thegleamingglass-and-concretehabitatspr
Europa’sWateryUnderworldEuropa,oneofJupiter’s63knownmoons,looksbrightandicyonthesurface.Butappearancescan
RacialPrejudiceInsomecountrieswhereracialprejudiceisacute,violencehasbeentakenforgrantedasameansofsolving
随机试题
硫(S)属于气相型循环。()
A.心B.脾C.肺D.肾E.胃“君主之官”是指()
A.铅盐沉淀法B.胆甾醇沉淀法C.吉拉尔试剂法D.碱水提取法E.pH梯度萃取法
【背景资料】某装饰公司承接了某装饰工程并编制了网络计划,如下图所示:甲乙双方约定6月15日开工,在工程施工中发生了如下事件:事件一:由于开工手续的原因,致使工作B推迟了2d。事件二:6月21日~6月22日,整个施工现场停电2d。【问题】编制
我国现行税法规定,在采用核定征收方式对个人独资企业的生产经营所得征收个人所得税时,如果企业经营多业,则无论其经营项目是否单独核算,均应根据其主营项目确定其适用的应税所得率。()
在一次运动员选拔中,对人员选拔有如下要求:①或者选拔陈橙或者选拔李墨。②如果选择陈橙,则不能选拔吴蓝,③只有选拔吴蓝,才选拔林青。④李墨,林青只能选择一人。由此可见,下列哪项正确体现了这次运动员的选拔方案?
设0<a<1,区域D由x轴,y轴,直线x+y=a及x+y=1所围成,且
Java语言提供了byte、______、int、long四种类型的整型变量。
使用VC++2010打开考生文件夹下prog1中的解决方案。此解决方案的项目中包含一个源程序文件prog1.c。在此程序中,规定输入的字符串中只包含字母和木号。请编写函数fun,其功能是:使字符串的前导*号不得多于n个,若多于n个,则删除多余的*号;若少于
Itisnaivetoexpectthatanysocietycanresolveallthesocialproblemsitisfacedwith______.
最新回复
(
0
)