Question

1. what is the difference between the molecules of a compound? 14. which changes in matter can produce an atom different from the original?

Explanation:

1. Atoms are the basic units of elements, while molecules of a compound are made up of two or more different - type atoms chemically bonded together. For example, a water molecule ($H_2O$) is composed of two hydrogen atoms and one oxygen atom, while a hydrogen atom ($H$) is an individual atom of the element hydrogen.
2. Nuclear changes such as nuclear fission and nuclear fusion can produce an atom different from the original. In nuclear fission, a heavy - nucleus splits into lighter nuclei, and in nuclear fusion, light nuclei combine to form a heavier nucleus, changing the atomic species.

Answer:

1. Atoms are basic units of elements, and compound molecules are composed of different - type atoms bonded.
2. Nuclear changes (nuclear fission and fusion).