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
96
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
Theindexisthegovernment’schiefgaugeoffutureeconomicactivity.
DungtoDeathFieldsacrossEuropearecontaminatedwithdangerouslevelsoftheantibioticsgiventofarmanimals.Thedrugs,w
HighwaysintheUSTheUnitedStatesiswell-knownforitsnetworkofmajorhighwaysdesignedtohelpadrivergetfromoneplac
ThanksgivingDayTheAmericanThanksgivingDaycelebrationgoesbackto1621.Inthatyear,aspecialdinnerwaspreparedinPly
LookingtotheFutureWhenamagazineforhigh-schoolstudentsaskeditsreaderswhatlifewouldbelikeintwentyyears,t
A.rarelyissuccesssomysteriousB.largerewardsfollowC.IeliminatethecandidateD.weshoulddropthemandmovetosometh
Canyougiveaconcreteexampletosupportyouridea?
A.itsdetectingpowerB.millionsoflightyearsawayinspaceC.thelocationoftheVLTD.asanexampleE.thebirthofthe
Thefatherwasunwillingtogivehissonthekeystohiscar.
Frommystandpoint,youknow,thisthingisjustridiculous.
随机试题
杨绛(1911一),女,生于北京,原籍江苏无锡。曾翻译世界名著______、______等。代表作有散文______、______,长篇小说______等。
抗精神病药引起的严重的不良反应有()
患者女,39岁。因“右侧咽喉部疼痛4个月”就诊。查体:右侧扁桃体区可见外生型新生物,右下颌下可及一质硬固定的1.5cm×2cm大小包块,无压痛。经新生物活检确诊为扁桃体未分化癌。头颈部MR.I提示右扁桃体区可见3cm×3cm肿块局限于右侧扁桃体窝,右上颈可
一奶牛发情配种4个月后,直肠检查子宫未有妊娠变化,左侧卵巢有一充满液体、突出于卵巢表面的结构;母牛一直未有发情表现,但荐坐韧带松弛。则该病是
房地产经纪机构风险管理的第一步是()。
发包人与承包人因建设工程质量发生争议,双方同意交仲裁机构仲裁。仲裁机构作出裁决书后,发包人不服仲裁裁决并向法院起诉,则法院应当()。
下列哪项是健康保险公估的主要业务形式?( )
纳税人因特殊情况不能按照税法规定的纳税期限缴纳税款的,可以申请延期缴纳税歉。下列各项中属于特殊情况的有()。
3,3,4,5,7,7,11,9,(),()
根据下列资料,回答问题。2016年年末,纳人统计范围的全国各类文化(文物)单位31.06万个,比上年年末增加1.15万个;从业人员234.81万人,同比增加2.34%。其中,各级文化文物部门所属单位66029个,增加319个;从业人员66.10万人。增加
最新回复
(
0
)