西安电子科技大学考博英语模拟真题及其解析.pdfVIP

中国考博辅导首选学校 西安电子科技大学考博英语模拟真题及其解析 One of the simplest and best know kinds of crystal is the ionic salt,ofwhichatypicalexample issodiumchloride,orordinarytable salt.The fundamental components of a ionic salt are ions:atoms or molecules thathave become electrically chargedby gaining or losing one more electrons. I forming sodium chloride, for example, sodium atoms give up a electro (therebybecoming positively charged) and chlorineatomsgai a electro (therebybecomingnegativelycharged). The ionsare attracted to one another by their opposite charges, and they stack together compactly, like tightly packed spheres. Recently, scientists at Michiga State University created a new kind of crystal called a electride. I electrides, the anions Geng duo yua xiao wa zheng kao bo ying yu zhe ti ji qi jie xi qing lia xi qua guo mia fei zi xu dia hua: si ling ling liu liuba liu jiu qi ba ,huo jia zi xu qq: qi qi er liuqi ba wu sa qi (negativeions) are completelyreplaced by electrons,which are trapped i naturally formed cavities withi a framework of regularly stacked cations (positiveions).Electrides are the first examples of ionic salts i which all these anionic sites are occupied solely by electrons. Unlike other types of anions, anionic electrons do not behave as iftheywere simple charged spheres. I particular, because of their low mass and their tendency to interactwith one another over great distances,theyca otbe “pi eddow ”toanyonelocation.Instead, theywanderclosetoandamongtheatomsliningthecavityandinteract with electrons i nearbycavities,perhapschangingplaceswith them. 中国考博辅导首选学校 The properties of a electride depend largely o the distance betwee the cavities that hold trapped electrons. Whe the trapped electronsare farapart, theydonot interactstrongly,and sobehave somewhat like a array of isolated negative charges. Whe they are closer t