Understanding Atomic Structure

Atoms are the fundamental building blocks of matter. They consist of a nucleus containing protons and neutrons, surrounded by electrons that occupy various energy levels. Each atom has unique properties determined by the arrangement of its electrons. When an atom gains or loses electrons, or when protons and neutrons are involved in nuclear reactions, the atom may change its charge or become a different isotope. In atomic physics, understanding the structure and behavior of atoms is crucial for various applications, including nuclear energy, radiation therapy in medicine, and the development of new materials.

Which of the following statements correctly describes a characteristic of atomic structure?