Protons are positively charged subatomic particles found in the nucleus of an atom. They play a crucial role in determining the atomic number, which defines the element. For example, a hydrogen atom has one proton, while a carbon atom has six. The number of protons in an atom influences its chemical properties and behavior. Protons are held together in the nucleus by the strong nuclear force, which overcomes the repulsion between their positive charges. This force is essential for the stability of atoms. Additionally, protons can participate in various nuclear reactions, such as those occurring in stars, where they fuse to form heavier elements, releasing energy in the process.