问题 选择题

X、Y、Z、W为四种短周期元素.X元素的原子最外层电子数是核外电子层数的3倍;Y元素的最高正价与最低负价的代数和为6;Z在地球中的含量仅次于氧;Y、Z、W同周期,W的常见化合价为+2价.下列说法不正确的是(  )

A.存放W单质的仓库失火不能用CO2灭火

B.Z的氧化物熔化时破坏分子间作用力

C.原子半径由到小的顺序为W>Z>Y>X

D.与X同主族元素的氢化物中,X的氢化物沸点最高

答案

X、Y、Z、W为四种短周期元素.X原子最外层电子数是核外电子层数的3倍,则X为氧元素;Z在地球中的含量仅次于氧,则Z为硅元素;Y元素的最高正价与最低负价的代数和为6,则Y的最高价为+7价,为短周期元素,所以Y为氯元素;Y、Z、W同周期,W的常见化合价为+2价,则W为镁元素.

A、镁能与二氧化碳反应生成碳与氧化镁,故存放W单质的仓库失火不能用CO2灭火,故A正确;

B、Z的氧化物是二氧化硅,属于原子晶体,熔化时破坏原子间共价键,故B错误;

C、同周期元素从左到右原子半径逐渐减小,最外层电子数目相差不大电子层越多,原子半径越大,则原子半径由小到大的顺序为O<Cl<Si<Mg,即W>Z>Y>X,故C正确;

D、氧族元素的氢化物分中,H2O含有氢键,沸点较高,故D正确.

故选:B.

阅读理解

It has been argued that an infant under three who is cared for outside the home may suffer because of the separation from his parents.The British psychoanalyst John Bowlby believes that separation from the parents during the sensitive "attachment" period from birth to three may scar (留下疤痕) a child's personality and incline to emotional problems in later life.Some people have drawn the conclusion from Bowlby's work that children should not be sent to day care before the age of three, and many people do believe this.But there are also arguments against such a strong conclusion.

Firstly, anthropologists (人类学家) point out that the hidden love between children and parents found in modem societies does not usually exist in traditional societies.For example, we saw earlier that among the Ngonis the father and mother of a child did not raise their infant alone.But traditional societies are so different from modern societies that comparisons based on just one factor are hard to understand.

Secondly, common sense tells us that day care would not be so widespread today if parents and caretakers found that children had problems with it.But Bowlby's analysis raises the possibility that early day care has delayed effects.The possibility that such care might lead to more mental illness or crime 15 or 20 years later can only be noticed by the use of statistics.Statistical studies of this kind have not yet been carried out, and even if they were, the results would be certain to be complicated and controversial.

Thirdly, in the last decade, there have been a number of careful American studies of children in day care, and they have reported that day care had a neutral of slightly positive effect on children's development.But tests that have had to be used to measure this development are not widely enough accepted to settle the issue.

小题1:This passage is mainly talking about________.

A.children's personality

B.advantages of infants' early care

C.infants' education

D.negative effect of infant school小题2:The phrase "day care   in the first paragraph probably means_____.

A.nursing school

B.baby-sitter

C.boarding school

D.primary school小题3:According to Bowlby, children under the age of three______.

A.should not be sent to school

B.should be cared for outside the home

C.will not suffer fro m parental separation

D.don't mind who will look after them小题4:The argument against Bowlby's conclusion shows that___.

A.children have problems with day care

B.there is no negative effect on infants who go to school before three

C.there is a long-term effect on infants who go to school before three

D.children who are sent to school before three are sent to mental illness

多项选择题