来自侯连尝的问题
默写出元素周期表中前20号元素符号和名称.___、___、___、___、___、___、___、___、___、___、___、___、___、___、___、___、___、___、___、___.
默写出元素周期表中前20号元素符号和名称.
___、___、___、___、___、___、___、___、___、___、___、___、___、___、___、___、___、___、___、___.

