问题 填空题

金属晶体是面心立方体,立方体的每个面5个金原子紧密堆砌(如图其余各面省略),金原子半径为d m,求

(1)金晶体中最小的一个立方体含有__________个金属原子。

(2) 欲计算一个晶胞的体积,除假定金原子是刚性小球外,还应假定         ;

(3)计算一个晶胞的体积是                     cm3

(4)金的密度为_________g•cm-3

(5)列式计算金原子的空间利用率                                   

答案

(1)4        (2) 立体各面上对角线上的球相切 (3)16  d3×106

(4)197/4N d3×106    (5)

(1)根据面心立方体的晶胞结构可知,含有的原子有8×1/8+6×1/2=4。

(2)还应假定立方体各面上对角线上的球是相切的。

(3)设立方体的边长是x。因为面对角线的是4d m,所以边长x=2m。因此一个晶胞的体积是x3=16  d3×106 cm3

(4)1个晶胞的质量是,所以密度是

(5)4个金原子的体积是                                ,所以金原子的空间利用率为

选择题
阅读理解

阅读理解。

     Collecting information about (申请表) are closely connected, However, filling out an appheation

fornt is much easier because you have total control and have enough time to think and plan.

      That you are given a form to fill out does not necessarily mean that you have to answer all the

questions in it. If the form contains unclear questions or lerms and conditions, you can make some

changes before signing (签约) it, or refuse to answer some of the questions. What you must realize

is that those terms and conditions have been written by highly paid lawyers. Each word is important,

or it would not be there; and you can be sure that there is not anything there that is written with your

interests in mind.

     I know what I speak of because, as a lawyer for Litton Industries. I wrote the terms and conditions

that were printed on the back of order forms, I wrote the most tiring terms and conditions anyone has

ever seen. Still, 90 percent of the buyers would just sign on them without questioning anything, If anyone

questiones them. We would reach an agreement on something that was acceptable to both siders.

     So when you see a preprinted application that contains questions or terms and conditions, read it all and

read it slowly. If you don't like something, you can simply change the parts you don't like, Remember that

everything can be settled by discussion. To what degree it can be settled depends on your position (立场),

of course, and that is something only you can determine.

1. Filling out application forms is much "easier" because _____.

A. everything connected with application forms is easier

B. it is easier to collect information about pre-employment

C. you can plan and have control of the needed time

D. you can control the form filling with enough time

2. We can learn from the underlined part "Each word is important" that _____.

A. everything in a form must be read carefully

B. questions in a form must be answered

C. the conditions that interest you are changeable

D. something of your interests is most important

3. The writer points out with an example that the side who will sign a form _____.

A. it depends on your position to settle everything in a form

B. questions in a form are more important than your position

C. you have little right to determine the conditions you like most

D. you must change a preprinted application before it is discussed

4. It can be inferred from the 4th paragraph that ________.

A. it depends on your position to settle everything in a form

B. questions in a form are more important than your position

C. you have little right to determined the conditions you like most

D. you must change a preprinted application before it is discussed