Which of the following is NOT one of the three main parts of an atom?

The three main parts of an atom are protons, neutrons, and electrons. Protons and neutrons are found in the nucleus at the center of the atom, while electrons orbit around the nucleus in various energy levels. Each of these components has a specific role: protons carry a positive charge, electrons bear a negative charge, and neutrons are neutral and contribute to the mass of the atom.

Quarks, on the other hand, are fundamental particles that make up protons and neutrons. They combine to form these larger particles, but quarks themselves are not considered a part of the atom in the same way as protons, neutrons, and electrons. Hence, they do not fit into the category of the three main parts of an atom, which is why this option is correct. Understanding the structure of an atom is essential for studying chemical reactions and the behavior of elements in different states of matter.