用化学用语表示：
（1）2个氢原子 ；
（2）一个镁离子 ；
（3）氧化铁中铁元素化合价显+3价 ．
（1）2H；（2）Mg2+；（3）
2O3．
题目分析：（1）由原子的表示方法，用元素符号来表示一个原子，表示多个该原子，就在其元素符号前加上相应的数字，故2个氢原子表示为：2H．
（2）由离子的表示方法，在表示该离子的元素符号右上角，标出该离子所带的正负电荷数，数字在前，正负符号在后，带1个电荷时，1要省略．若表示多个该离子，就在其元素符号前加上相应的数字，故一个镁离子可表示为：Mg2+．
（3）由化合价的表示方法，在其化学式该元素的上方用正负号和数字表示，正负号在前，数字在后，故氧化铁中铁元素化合价显+3价可表示为：2O3．
点评：本题难度不大，主要考查同学们对常见化学用语（原子符号、化合价、离子符号等）的书写和理解能力．
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| This is Red Star Town. My grandfather has lived here all his life. He 1 my grandmother here and they got married. Red Star Town was called Taping Town before. The government started 2 the wooden houses in this area when the Red Star Town underground station was built. 3 June 2000, Taping Town has become a history. My grandfather missed many things about Taping Town. 4 in the small town knew him well. They all liked him because he used to be a good 5 in a hospital. Now he is old and stays at home. In the past, there were 6 stone and wooden houses around here. Also, there were many big trees. Now new 7 are here and there. The streets are wide and clean. There are all kinds of shops and you can buy anything 8 . My grandfather is happy that life has improved so much, 9 he still feels lonely because he really misses everything in the past. Many of his friends moved away because the government let them 10 in new apartments in new towns. The old town is still beautiful in his heart though it has disappeared (消失). | ||||
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