题目

下列化学符号书写正确的是（  ） A．两个水分子﹣2H2OB．氯化铝﹣AlClC．两个氯原﹣Cl2D．正二价的铜元素﹣Cu2+   答案：考点：化学符号及其周围数字的意义． 专题：化学用语和质量守恒定律． 分析：本题考查化学用语的意义及书写，解题关键是分清化学用语所表达的对象是分子、原子、离子还是化合价，才能在化学符号前或其它位置加上适当的计量数来完整地表达其意义，并能根据物质化学式的书写规则正确书写物Ⅲ. 语法填空[2015 •广东肇庆第二次统一检测]阅读下面材料，在空白处填人适当的内容（1个单词）或括号内单词的正确形式。Umbrella is what we easily forget and leave behind in our daily life. When the weather is fine, we certainly don't think of it; only when it's raining, we'll carry it purposefully. But as soon as the rain stops, most likely we'll forget 10. we've put it.   It has to wait patiently and pitifully for11._____ owner to claim it, otherwise it'll remain alone as a deserted umbrella.Once I suddenly found my long-time 12.____(use) umbrella "disappeared". I really got lost and regretted quite some time 13._____ my own carelessness.Several days later, out of my 14._____(expect) ， I saw it quietly stand in a corner of the house where I worked. I was extremely glad to regain it. Looking carefully at it,though it was so familiar 15.________me,Ifoundforthefirsttimeitswoodehandle   16.______(wear)out as a result of repeated rain-wash for years. I sought for it only when I needed it.   It occurred to me that I should have paid17. _________ (much) attention to it.It sets me thinking. Around us there are always people giving us support in silence just like 18. umbrella that protects us from the rain or any wretched weather. Will you think of those individuals 19._____have helped you get through difficulty when you are leading a comfortable life?