用化学符号或符号表示的意义填空:
①2个磷原子____;
②Al3+____;
③三个硫酸根离子____
④5个水分子____;
⑤NO2中N元素显+4价____.
⑥氯化亚铁____.
选出与听到的内容相符的图片( )
—Although my son failed the exam, he tried his best to________
— He is old enough to control his feelings.