下表为元素周期表的一部分，请参照元素在表中的位置，回答下列问题（凡能用化学用语的必须用相应的化学用语回答）：

（1）用原子符号表示中子数为8的编号为③的原子____，以上元素中原子的电子层数等于最外层电子数的元素为____，⑤、⑥、⑦、⑧三元素的简单离子半径由大到小的顺序为         。

（2）②①④三种元素能按原子个数比1：2：1形成一种在室内装修过程中常见的气体污染物。该气体分子的中心原子的杂化轨道类型为____，1mol该分子中π键的数目为____。

（3）写出⑥的单质在④的单质中燃烧产生的化合物的电子式         ，该化合物与足量⑨的低价硫酸盐溶液反应的离子方程式               。

（4）同主族元素的单质及化合物在许多性质上都存在着递变规律。下图是①、⑤、⑧、⑩的单质及①分别和⑤、⑧、⑩形成的化合物的键能大小。

由图中键能数据推断得知：①—R键（R表示⑤、⑧、⑩）的键能随分子中键长的增长而   （填“增大”或“减小”）。同主族元素随着原子序数的递增，非金属元素的单质分子中化学键的键长逐渐增大，键能____（填“一定减小”或“不一定减小”）根据图中键能数据，写出①的气态单质在⑧的气态单质中燃烧的热化学方程式____。

阅读理解。

     Except for the Indians, the earliest backpackers in America were frontiersmen (边疆居民), who walked in

the wilderness looking either for necessities such as food and water or for sources of wealth such as fur and

gold. For them backpacking was a way of survival or a means of achieving what one day would be called the

"American dream". Today, however, many people enjoy backpacking as a recreational activity. Shouldering a

pack and leaving behind the world of telephone, television and traffic promise an exciting experience. Testing

one's stamina (耐力) and skills and challenging a sense of one's place in the natural world can be rewarding.

Moreover, backpacking is an activity that can last any length for time and can be enjoyed alone or with friends.

Then too, a backpacking trip may be organized within a day or two. The backpacker and his friends have only

to decide on their destination and then organize the all-important kit (工具包), whose contents they must depend

on throughout their trip. A map, a compass, a flashlight, along with first-aid equipment, food, and extra clothing

can be rounded up without much difficulty. Once the backpackers have left word about where they go in a note

on the refrigerator door or in a message on an answering machine, they can look forward to an adventure that

will lift the spirit and encourage the soul. Their outing will enable them to return in a short time to the age of

technology with the courage and independence of Natty Bumppo, who did indeed belong to the age of the

frontier.

1. The passage mainly discusses _____. 　[ ]

A. the early backpackers 　　

B. how backpacking started 　　

C. important tips on backpacking 　　

D. why people of today are interested in backpacking

A. had no recreation in life 　　

B. did backpacking for a living 　　

C. enjoyed backpacking very much 　　

D. had better skills than backpackers today  

3. It seems that the writer of the passage thinks that backpacking today is _____. 　　[ ]

A. a waste of time 　　

B. a great adventure 　　

C. a rewarding experience 　　

D. a means to achieve American Dreams

4. One of the advantages of backpacking is that _____. 　　[ ]

A. it is not so challenging as other activities 　　

B. it can help people to establish a link with nature 　　

C. it does not require people to decide on a destination 　　

D. it is a group activity and can cure a person's loneliness