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有核电荷数小于18的A、B、C、D四种元素，A元素的原子构成一种单质，可以和黏土混合制成铅笔芯；B单质的体积在空气中占21%；C原子有3个电子层，最外层与最内层电子数相同；B原子比D原子少一个电子层，它们可以形成DB 2 和DB 3 两种化合物． （1）写出这四种元素的名称：A ______，B ______，C ______，D ______． （2）写出A、B形成化合物的化学式 ______． （3）D单质在B单质中燃烧时的化学方程式 ______，其生成物对环境的破坏是形成 ______． （4）A、C、D分别与B形成的化合物可以统称为 ______． （5）B、C和D三种元素形成的化合物的化学式是 ______．
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returns
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knowledge
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