写作要求：（1）中心突出，内容充实。（2）感情真挚，语言流畅。（3）字迹工整，书写规范。（4）文体不限，字数不少于600字。

两个氢原子____； 氖气____；两个铵根离子____；氧化镁中镁元素的化合价____；氯化钠中的阳离子____．

阅读短文，从方框中选择适当的单词填空                                                                    

       Changqing has a long history but it is the new district of Jinan. It ____  in the west of Jinan. and covers 1178 square kilometers. The ____  of Changqing is about 530,000. It has convenient transportation ____  it's easy to get here. There are many ancient places of interest for you to visit, such as Lingyan Temple, Xiaotang Hill and so on. It has changed a lot since it became the new district of Jinan. Now it has 15 colleges or universities. You can make your ____ come true there. And the Expo garden which was built newly attracts thousands____ visitors every year. Welcome to Changqing, and you will enjoy yourself.

一根桃树枝上开了四朵桃花，它们分别被害虫吃掉了花瓣、花萼、雄蕊和雌蕊，这一枝条上最多可结几个桃子（　　）