问题 问答题

下列化学用语书写正确的是(  )

A.NH3分子的结构式:

B.CO2分子模型的示意图:

C.乙烯分子的结构简式:CH2CH2

D.Na2O的电子式:

答案

A、NH3分子中氮原子最外层5各电子,有三个单电子,与氢原子结合时形成三个共价键,故A正确;

B、二氧化碳分子结构是直线型,选项中的模型中原子的相对位置不对,故B错误;

C、乙烯分子的结构简式中的双键不能省略,故C错误;

D、氧化钠是由钠离子和氧离子构成,电子式的书写两个钠离子不能合并,选项中的电子式不能正确表述得失电子关系,故D错误;

故选A.

完形填空

Thousands of years ago,human(人类)didn’t live in towns.Sometimes they would live in caves(洞穴)or build camps in the forest.

Only about thirty people  1   in each camp.The men would go hunting while the woman and children  2 food from trees around the camp.All the food was  3 among people in the group.Every few weeks they moved to another place to find more food.It was a simple life,but people had to be  4They had to make everything that they needed,and they had to know a lot about plants and animals.

Nowadays most people live in towns and cities,and they work in offices and factories.Life isthan in the old days.There are fewer  6 ,but there is less excitement.Some people go  7 excitement  sailing round the world.climbing mountains,or exploring(探测)caves.

Most people look forward to the  8 ,a time when they can enjoy a change from the normal life.For some this means going camping.But camping today is  9 from camping in the past.Gas cookers,ready-made food and air-beds mean people can camp much more  10 than they did in the old times.

1.A.lived         B.talked       C.came        D.danced

2.A.planted       B.collected     C.watched     D.bought

3.A.found        B.used         C.shared      D.sold

4.A.polite        B.kind         C.calm       D.clever

5.A.worse        B.faster        C.easier       D.harder

6.A.dangers       B.stories       C.people      D.animals

7.A.waiting for    B.looking for    C.turning on   D.putting on

8.A.dreams       B.gifts         C.meals       D.holidays

9.A.away        B.different       C.free        D.far

10.A.slowly       B.terribly        C.comfortably  D.hopefully

单项选择题