下列说法正确的是 A．第ⅠA族元素的金属性比第ⅡA族元素的金_爱下问搜题

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问题选择题

下列说法正确的是

A．第ⅠA族元素的金属性比第ⅡA族元素的金属性强

B．第ⅥA族元素的氢化物中，稳定性最好的其沸点也最高

C．同周期非金属氧化物对应水化物的酸性从左到右依次增强

D．第3周期元素的离子半径从左到右逐渐减小

答案

答案：B

A项中同周期的第ⅠA族和第ⅡA族的金属元素比较，第ⅠA族的元素比第ⅡA族的元素的金属性强，但不同周期的是无法比较的，如Ca的金属性比Na的金属性强；B项中同主族元素氢化物的沸点随相对分子质量的增大而升高，但由于氢键的存在，H₂O的沸点是该族氢化物中最高的，稳定性也是最好的；C项在比较非金属氧化物对应水化物的酸性时，一定要是最高价含氧酸才可以比较；D项第3周期中原子半径从左到右是逐渐减小的，但在形成离子时Na^＋、Mg²^＋、Al³^＋比其原子少了一个电子层，而S²^－、Cl^－电子层并不变，仍是3层，所以同周期元素的阴离子半径大于阳离子半径。

单项选择题

裸露病毒的结构是

A．核酸＋包膜
B．核酸斗衣壳＋包膜
C．衣壳＋包膜
D．核酸＋衣壳
E．核酸＋包膜＋外膜

单项选择题案例分析题

Shopping habits in the United States have changed greatly in the last quarter of the 20th century. （1） in the 1900s most American towns and cities had a Main Street. Main Street was always in the heart of a town. This street was （2） on both sides with many （3） businesses. Here, shoppers walked into stores to look at all sorts of merchandise: clothing, furniture, hardware, groceries. （4）,some shops offered （5） .These shops included drugstores, restaurants, shoe-repair stores, and barber or hairdressing shops. （6） in the 1950s, a change began to （7） .Too many automobiles had crowded into Main Street （8） too few parking places were （9） shoppers. Because the streets were crowded, merchants began to look with interest at the open spaces （10） the city limits. Open space is what their car-driving customers needed. And open space is what they got （11） the first shopping centre was built. Shopping centres, or rather malls, （12） as a collection of small new stores （13） crowded city centres. 14 by hundreds of free parking space, customers were drawn away from （14） areas to outlying malls. And the growing （16） of shopping centres led （17） to the building of bigger and betterstocked stores. （18） the late 1970s,many shopping malls had almost developed into small cities themselves. In addition to providing the （19） of one stop shopping, malls were transformed into landscaped parks, （20）benches, fountains, and outdoor entertainment.

请在13处填上正确答案（）

A.out of

B.away from

C.next to

D.near