What is the main structural component of an atom?

The nucleus containing protons and neutrons is indeed the main structural component of an atom because it forms the central core that contains most of the atom's mass. Protons carry a positive charge, while neutrons are neutral, contributing to the overall stability of the nucleus. The nucleus is surrounded by a cloud of electrons, which occupy various energy levels around it, but it is the nucleus that serves as the defining structure, housing almost all of the atom's mass and determining its identity (through the number of protons, which defines which element an atom represents).

In contrast, electrons, while critical to the behavior of atoms and molecules, are not considered a structural component in the same way the nucleus is, as they occupy space around the nucleus and are much less massive. A cloud of energy is more of a conceptual model used to describe electron behavior rather than a physical part of the atom's structure. Finally, only protons within the nucleus does not capture the presence of neutrons, which are equally important for the stability of the atom. This makes the nucleus essential for defining the structure and properties of an atom.