短周期元素W、X、Y、Z的原子序数依次增大,且原子最外层电子数之和为14。W的原

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问题:

短周期元素W、X、Y、Z的原子序数依次增大,且原子最外层电子数之和为14。W的原子半径比X的大,X原子的最外层电子数是内层电子数的2倍,元素Y是地壳中含量最高的金属元素,Z原子的最外层电子数是其电子层数的2倍。下列说法正确的是

A.元素X的最高价氧化物对应的水化物的酸性比Z的弱

B.元素Y、Z的简单离子的电子层结构相同

C.元素W与Z形成的化合物为共价化合物

D.原子半径由大到小的顺序为:r(Z)>r(Y)>r (W)

考点:构成物质的粒子—分子、原子、离子元素周期律
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大气中臭氧浓度的减少是由于臭氧的形成与分解速率不相同引起的。( )

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In one sense, we can trace all the problems of the American city back (91) a single starting point: we Americans don’t like our cities very much.
That is, on the (92) of it, absurd. After all, more than three-fourths of us now live in cities, and more are (93) to them every year. We are told that the problems of our cities are (94) more attention in Washington, and scholarship has discovered a whole new (95) in urban studies.
(96) , it is historically true: in the American psychology, the city has been a basically suspect institution, (97) with the corruption of Europe, totally lacking that sense of spaciousness and innocence of the (98) and the rural landscape.
I don’t pretend to be a scholar on the history of the city in American life. But my thirteen years in public (99) , first as an officer of the U. S. Department of Justice, then as Congressman, and now as Mayor of the biggest city in America have taught me (100) too well the fact that a p antiurban attitude (101) consistently through the mainstream of American thinking. Much of the (102) behind the settlement of America was in reaction (103) the conditions in European industrial centers and much of the theory (104) the basis of freedom in America was linked directly to the availability of land and the perfectibility of man outside the corrupt influences of the city.
What has this to do with the predicament of the modern city I think it has (105) to do with it. For the fact is that the United States (106) the federal government, which has historically established our national priorities, has simply never thought that the American city was "worthy" of (107) —at least not to the (108) of expending any basic resources on it.
Antipathy to the city predates the American experience. When industrialization (109) the European working man into the major cities of the continent, books and pamphlets appeared (110) the city as a source of crime, corruption, filth, disease, vice, licentiousness, subversion, and high prices.

A.flocking

B.gathering

C.collecting

D.flying

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临床上发病率最高的颈椎病是哪个类型()

A.脊髓型

B.神经根型

C.交感神经型

D.椎动脉型

E.混合型

题型:选择题

扑灭电气火灾时应注意哪些?

题型:选择题

票据具有无因性,是指不是出于出票人本人意愿的行为,如偷窃获得票据也属于出票行为。( )

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