The Heart of the Atom: The Nucleus

The nucleus is the extremely small, dense region at the very center of an atom. Discovered by Ernest Rutherford in 1911, we now know that while the atom is mostly empty space, the nucleus is the 'command center.' It is held together by the strong nuclear force, which is the most powerful force in nature. This force is necessary because it overcomes the tendency of positively charged particles to push each other away. Without the nucleus, matter as we know it would simply fly apart!

Inside the nucleus, you will find two types of particles collectively called nucleons. First are protons, which carry a positive electrical charge of $+1$. The number of protons is like an atom's fingerprint; it defines which element the atom is. For example, any atom with exactly $6$ protons is Carbon. The second residents are neutrons. These particles are neutral, meaning they have a charge of $0$. Neutrons act like 'nuclear glue,' helping to stabilize the protons within the tight space of the nucleus.

Why is the nucleus so heavy? It comes down to the mass of the particles. We measure subatomic particles in Atomic Mass Units (amu). Both protons and neutrons have a mass of approximately $1$ amu. In contrast, the electrons orbiting outside the nucleus are tiny, with a mass of only about $\frac{1}{1836}$ amu. Because protons and neutrons are so much larger than electrons, the nucleus accounts for nearly all the mass of the atom, even though it occupies almost no space.