atoms
An atom is the smallest amount of a substance that can take part in a chemical reaction.
the news that Einstein's former colleagues Otto Hahn and Fritz Strassmann had split the atom.
爱因斯坦的前同事奥托·哈恩和弗里茨·斯特拉斯曼分裂了原子这一消息。
A methane molecule is composed of one carbon atom attached to four hydrogen atoms.
甲烷分子是由一个碳原子和四个氢原子构成的。