问题 选择题

X、Y、Z、M、W为五种短周期元素。X、Y、Z是原子序数依次递增的同周期元素,且最外层电子数之和为15,Y与M形成的气态化合物在标况下的密度为0.76g·L-1;W的质子数是X、Y、Z、M四种元素质子数之和的1/2。下列说法正确的是

A.由X、Y、Z、M四种元素形成的化合物一定有共价键

B.原子半径:W>Z>Y>X>M

C.由X元素形成的单质一定是原子晶体

D.XZ2、X2M2、W2Z2均为直线型的共价化合物

答案

答案:A

题目分析:由题意可知:X是C,Y是N,Z是O,Y与M形成的气态化合物的相对分子质量为:0.76×22.4=17.则M是H,该化合物是NH3。因为W的质子数是X、Y、Z、M四种元素质子数之和的1/2,所以W的质子数是(6+7+8+1)÷2=11.W是Na元素。A.由C、N、O、H四种元素形成的化合物可以是NH4HCO3或(NH4)2CO3.这两种化合物中都含有离子键、共价键。故A选项正确。B.对于电子层数不同的元素来说,电子层数越多,原子半径越大;对于电子层数相同的元素来说,原子的核电荷数越大,原子半径就越小。该原子半径的大小顺序是:Na>C>N>O>H,B选项错误。C.由C元素形成的单质可能是金刚石、石墨、C60等金刚石是原子晶体,石墨是属于过渡型晶体,C60属于分子晶体,C选项错误。D.CO2、C2H2为直线型的共价化合物,Na2O2属于离子化合物,D选项错误。

阅读理解

阅读理解

     One morning, Mr Smith comes into the garden at the back of his house. He sees much snow in the

garden. He wants to drive his car out, so he asks a man to clean the road from the garage(车库) to the

gate. He says to the man, "Don't throw any snow on that side. It will damage(损坏) the flowers in my

garden, and don't throw any on the other side, for it will damage the wall and don't throw any into the

street, or the policeman will come." Then he goes out.

     When Mr Smith comes back, the road is clean. There is no snow on the flowers, on the wall or in the

street. But when he opens the garage to get his car out, he sees the garage is full of snow and the car is

under the snow.

1. One morning, Mr Smith finds _____ is full of'snow.

A. his garage    

B. his car          

C. his garden        

D. his house

2. He wants a man to clean the road because           .

A. he doesn't like snow

B. he often asks the man to do it

C. he has no time to clean the road

D. he wants to drive his car out of the garage

3. Where does Mr Smith tell the man to throw the snow in the garden?

A. On the wall.                    

B. On the flowers.

C. We don't know.                  

D. Into the street.

4. When Mr Smith opens the garage, _       .

A. he finds it is full of snow          

B. he takes the snow out

C. he finds there is no car there        

D. he takes his car out

5. Mr Smith's car is           .

A. in the street

B. under the snow from the road

C. in front of his house

D. near the road

填空题