问题 选择题

下列比较正确的是( )

A.离子半径:Al3>O2

B.与水反应的激烈程度:Al>Mg

C.热稳定性:HF>NH3

D.单质的氧化性:S>O2

答案

答案:C

题目分析:核外电子排布相同的微粒其微粒半径随原子序数的增大而减小,A不正确,离子半径:Al3<O2;同周期自左向右,金属性逐渐减弱,非金属性逐渐增强,所以选项B不正确,与水反应的激烈程度:Al<Mg。非金属性越强,氢化物的稳定性越强,C正确;同主族自上而下非金属性逐渐减弱,则选项D不正确,单质的氧化性:S<O2,答案选C。

点评:该题基础性强,侧重对学生基础知识的巩固和训练,有利于培养学生的逻辑推理能力和发散思维能力。该题的关键是明确元素周期律的含义,然后结合题意灵活运用即可。

完形填空

根据短文内容,从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。

“The chair is out to kill us,” says James Levine, a professor at the Mayo School of Medicine. Most of us have years of sitting experiences, considering ourselves quite good at it. ___小题1:____But unfortunately ,a good deal of data suggests that we’re off our chairs to spend so much time on the vast variety of other seats where we’re fond of parking our bottoms .Here are some things that scientists have learned about the insidious (阴险的)nature of sitting.

Sitting position has gone wrong . 

The human body is designed for walking. ____小题2:___ But lately, not so much. In general, scientists believe ,Americans now sit for more than half of their walking hours .Sadly ,the sitting position exerts force on the body which can lead to a lot of trouble including poor circulation (血液循环) ,aches and pains.

____小题3:___

We’re not using much energy when we’re sitting still. ___小题4:___ It is also just another way of saying “watch out for extra pounds .”It is mainly the chair that has caused the increase in obesity rates .A person with a desk job may burn 300 calories a day at work , but the same person might burn 2,300 calories a day in jobs that require considerable physical efforts. In other words , we need more walking to burn more calories.

Realize the damage.

Sitting at your desk and working hard for hours on end can increase your chances of getting a promotion. ____小题5:____ When comparing people who spent the most time sitting with those who spent the least time sitting, researchers found more sitting increases the risks of death from all causes.

A.Make people become too fat.

B.We will say nature intends us to do it.

C.They ought to work out to build their bodies.

D.But it also brings people diseases or even early deathE. Certainly people have done that for thousands of years

F. We should be more patient and work longer than before.

G. That is just another way of saying“we are not burning many calories”.

多项选择题