七年级下册英语周报第22期答案

35.[化学—物质结构与性质](1)1s2s2p53s23p3d04s24p2(2分)(2)干冰(1分);键(1分(3)CH4(1分)(4)F(1分);Ii(1分)(5)HC≡CH(2分)(6)2(2分);12(2分)1.76×10(7)NA·a3g·cm-3(2分)【解析】本题主要考査物质结构与性质,考査学生对物质结构的理解能力和综合运用能力。(2)干冰是分子晶体,足球烯是分子晶体,金刚石是原子晶体,石墨是介于分子晶体和原子晶体之间的混合型晶体。3)同主族元素从上至下原子半径逐渐増大,与氢形成的共价键键能逐渐减小,最简单气态氢化物的稳定性逐渐减弱。(5)含σ键与π键数目之比为3:2的物质为乙炔。6)硅晶体结构类似于金刚石,每个硅原子与周围四个硅形成共价键,而每个共价键被两个硅原子分摊:4×2;观察干冰晶体,与顶点上的二氧化碳分子最近距离的二氧化碳分子有3个,而每个二氧化碳分子被两个晶胞共用,有8×3×2=12个。(⑦)根据密度计算公式:1.76×1032g·cm")。NA·(10-10·a)3

第一节应用文One possible versionOur school held an art show entitled"Most Honored Worker"last week, to which our studentsand teachers gave an active responseThe works submitted came in different forms of photos, paintings and handcrafts. All of themtold vivid stories of the beauty of diligence and persistence in different walks of life. Those presentM,可at the show all gave a big applause to the works on display, saying that they learnt a lot from theseordinary but honorable workers

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