Atoms are the fundamental building blocks of matter. They were first proposed by the ancient Greek philosopher Democritus and were later studied in more detail by various scientists throughout history. The discovery of atoms paved the way for our understanding of the physical world and led to the development of atomic models.

At the heart of atomic structures are three basic components: protons, neutrons, and electrons. Protons carry a positive charge, neutrons have no charge, and electrons carry a negative charge. Protons and neutrons are located in the nucleus at the center of an atom, while electrons orbit around the nucleus in energy levels or shells.

To illustrate, let's consider the example of a helium atom. It consists of two protons and two neutrons in the nucleus, and two electrons orbiting around it in the first energy level. The number of protons determines the atomic number of an element, while the sum of protons and neutrons gives the atomic mass.

Overall, understanding atomic structure is essential for comprehending the behavior and properties of different elements in the periodic table.