At the most fundamental level, everything in the universe is made up of particles called atoms. Atoms, in turn, are made up of even smaller particles called protons, neutrons, and electrons. Protons and neutrons are found in the nucleus of the atom, while electrons orbit the nucleus. Atoms can combine with each other to form molecules, which are the building blocks of all matter. The properties of matter are determined by the arrangement of atoms and molecules within it. For example, the atoms in a solid are tightly packed together, while the atoms in a gas are more spread out. This difference in arrangement results in different properties, such as hardness and fluidity.
