题干

X、Y、Z、W是短周期主族元素,它们的原子序数依次增大。X原子最外层电子数是次外层的2倍,Y是地壳中含量最多的元素,Y原子最外层电子数是Z原子最外层电子数的2倍, W与Y同主族。下列说法正确的是(   )

A:X形成的单质只有一种

B:原子半径:r(W)>r(Z)>r(Y) >r(X )

C:常温下,Z单质可溶于W的最高价氧化物的水化物的浓溶液中

D:Y简单气态氢化物的热稳定性比W的强

上一题 下一题 0.0难度 选择题 更新时间:2016-03-23 06:26:35

答案(点此获取答案解析)

D

同类题3

   When you're not at home, many worries may start to crowd your mind. Did I turn the coffee maker off? Did I lock the door?Are the kids doing their homework or watching television? With a smart home, you can quiet all of these worries.

    A smart home is a home with a communication network. This network connects devices(装置), such as lights and TV sets, and allows them to be controlled from far away through electrical wiring, mobile phone communication or WiFi over the internet.

    More and more people may start to consider owning a smart home, because it makes life much more convenient. It can help keep your room at a certain temperature. It can record what happens inside the home and send the video to your phone. When you are on vacation abroad, you can use a smart home controller to switch on or off the electricity when necessary. Some smart homes can receive a visitor, allowing him to come in and offering him a drink. They can even feed the cat and water the plants.

    Besides, smart homes are easy to fix. Most smart home technology and devices are wireless and can be set up with a minimum of tools,using only the guiding information. When a problem appears,you can deal with it yourself without paying a professional.

    However, for home-users,the smart home technology is far from perfect.It can be rather expensive to own the technology and the devices. Also, because the smart home system(系统) allow its owner to get home information from anywhere, it leaves the home easy to be attacked by hackers(黑客), who may secretly use or change the information in the system.

    Now,many scientists are excited at the future of smart home technology. Imagine being able to get fashion advice from your mirror, or receive food shopping suggestions from your refrigerator. While there are others who worry that those smart devices will make people lazier and lonelier. Whatever it is, one thing is for sure---smart home technology will change the way we live and work.