题干

(1)下列物质中:互为同素异形体的有  ____  (填序号,下同),属于同位素的有  ____ ,属于同一种物质的有  ____ .
①液氯   ②1735Cl  ③白磷   ④氯气   ⑤红磷   ⑥1737​Cl
(2)下列物质中:只存在共价键的是  ____ (填序号,下同),只存在离子键的是  ____ ,既存在离子键又存在极性共价键的是  ____ ,既存在离子键又存在非极性共价键的是 ____ .
①Ar     ②CO2    ③Na2O2④KOH     ⑤MgBr2     ⑥NH4Cl     ⑦CaO    ⑧H2SO4
(3)用电子式表示MgBr2的形成过程: ____
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答案(点此获取答案解析)

③⑤,②⑥,①④,②⑧,⑤⑦,④⑥,③,

同类题4

阅读下面短文,掌握其大意,然后从各题所给的A、B、C和D项中,选出最佳选项。

         What happened to that brilliant idea that you once had? Did you  1  it because you thought that it was just a little thought? Have you ever   2 what that little thought would have become if you had acted on your instincts 3  if you had paid more attention to it?

         Imagine a   4  , where you are sitting at home watching television or reading a book, suddenly a light is   5  on in the dark tunnel of your mind as a thought or an idea crosses your mind. The thought   6   your attention but seems so meaningless and you are tempted to   7   it, but wait a minute! That thought could be the potential beginning of the   8   you have so much wished for.

         As the thought crosses your mind, your senses become alert and you suddenly see a possibility, a solution, or find the answer to a problem whose solution has  9    escaped you. It is almost as if a wise man has   10   the perfect solution into your ear or awakened your senses to a reality, thereby bringing light to your life. It is like finding the   11   piece of jigsaw puzzle(拼图游戏). This becomes an amazing moment and everything freezes around you as you excitedly try to grasp the practicality of that   12  but powerful thought.

         Your self­confidence and enthusiasm increase as you become  13   of the great possibilities that can   14   if that little thought is acted upon. This becomes the moment to build upon that thought and to put  15   any ideas that are streaming from that little thought for later review.   16   meaningless little thoughts or ideas, when acted 17,  have a potential to explode into great projects. Many successful projects have been 18   from the little positive thoughts that were carefully protected and recognized as bricks to great things.

         Don't waste a(n)   19  to act on a potentially brilliant idea. You don't have to wait for a major idea, or approval from your peers in order for you to act on that little thought.

         That little thought or idea is the  20  of great things if you decide to follow it through.