下列分子结构：CO2、CH4、PCl5、Na2O2、MgF2，其中原子的最外层不能都满足8电子稳定结构的是 ；属于离子化合物，且离子个数之比是2：1或1：2的是 。
PCl5、CH4、NaOH； Na2O2、MgF2
题目分析：PCl5、CH4、NaOH中磷元素、氢元素中原子最外层电子数均不能满足8电子稳定结构； Na2O2中需注意两个氧原子是以共价键的形式结合的，因此其中只含有一个阴离子，故“属于离子化合物，且离子个数之比是2：1或1：2的是Na2O2、MgF2”。
点评：此题属于基础题，也是易错题。易错点在于对Na2O2结构的不理解，需注意Na2O2中两个氧原子是以共价键的形式形成一个阴离子。
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| One evening I went to have dinner with my uncle and aunt. They had 1 invited another person, a young woman, so that there would be four people at 2 . Her face was familiar (面熟的). I was quite 3 that we had met 4 , but I could not 5 where I had seen her face. In the course of the talk, however, the young woman 6 to tell us that she had lost her purse the other day. All at once I remembered where I had seen her face. She was just the young girl in the photo in the purse I had picked up while walking down the street that afternoon, although she looked much older. She was 7 , of course, when I was 8 to describe her purse to her. Then I explained (解释) that I had recognized (认出) her from the photo I had found in the purse. My uncle insisted on going to the police station immediately to fetch the purse. As the policeman handed it 9 , he said I had found not 10 the purse, but the person who had lost it. | ||||
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