原子学

例句：

1. 1. The atom is the smallest unit of an element.
   原子是元素最小的单位。
2. 2. Atoms are made up of protons and neutrons.
   原子由质子和中子组成。
3. 3. The atom has a nucleus that contains the most stable form of matter.
   原子有一个核，包含最稳定的物质形态。