问题 选择题

右表为元素周期表前四周期的一部分,下列有关R、W、X、Y、Z五种元素的叙述中,正确的是

  
X   
WY R
  Z 
A. 常压下五种元素的单质中Z单质的沸点最高

B. Y、Z的阴离子电子层结构都与R原子的相同

C. W的氢化物沸点比X的氢化物的沸点高

D. Y元素的非金属性比W元素的非金属性强

答案

答案:D

题目分析:依据上图可以知道R、W、X、Y、Z分别为,Ar、P、N、S、Br。常温下Z的单质为溴,常温下为液体,而P和S的单质为固体,所以A错误;B中,Z的阴离子电子层结构与R原子的不相同,所以B错误,C中W的氢化物为PH3,X的氢化物为NH3,由于氨气能形成氢键,所以W的氢化物沸点比X的氢化物的沸点低,故C错误;根据同一个周期元素的非金属性从左往右逐渐增强,所以D正确。

点评:本题考查了元素周期表,该命题方式是高考命题的热点,该题难度适中。

单项选择题
单项选择题

Although there are many skillful Braille readers, thousands of other blind people find it difficult to learn that system. They are thereby shut (1) from the world of books and newspapers, having to (2) on friends to read aloud to them.

A young scientist named Raymond Kurzweil has now designed a computer which is a major (3) in providing aid to the (4) .His machine, Cyclops, has a camera that (5) any page, interprets the print into sounds, and then delivers them orally in a robot-like (6) through a speaker. By pressing the appropriate buttons (7) Cyclops’s keyboard, a blind person can "read" any (8) document in the English language.

This remarkable invention represents a tremendous (9) forward in the education of the handicapped. At present, Cyclops costs $ 50,000. (10) , Mr. Kurzweil and his associates are preparing a smaller (11) improved version that will sell (12) less than half that price. Within a few years, Kurzweil (13) the price range will be low enough for every school and library to (14) one. Michael Hingson, Director of the National Federation for the Blind, hopes that (15) will be able to buy home (16) of Cyclops for the price of a good television set.

Mr. Hingson’s organization purchased five machines and is now testing them in Maryland, Colorado, Iowa, California, and New York. Blind people have been (17) in those tests, making lots of (18) suggestions to the engineers who helped to produce Cyclops.

"This is the first time that blind people have ever done individual studies (19) a product was put on the market," Hingson said. "Most manufacturers believed that having the blind help the blind was like telling disabled people to teach other disabled people. In that (20) , the manufacturers have been the blind ones.

14()

A.settle

B.own

C.invest

D.retain