If an atom were a solar system, the proton is the bright, charged sun, and the electron is a tiny planet; the neutron acts as the invisible heavy anchor that holds the nucleus together without interfering with the electrical balance.

PANIC: Protons = Atomic Number (in charge), Neutron = (James) Chadwick.

The discovery occurred when beryllium atoms were struck by alpha particles ($^4_2\text{He}$), resulting in the emission of neutral radiation. Chadwick proved that these rays consisted of particles with a mass of roughly $1.675 \times 10^{-27} \text{kg}$ and zero electric charge. The nuclear reaction is represented as: $^9_4\text{Be} + ^4_2\text{He} \rightarrow ^{12}_6\text{C} + ^1_0\text{n}$.

Remember that while protons determine the element identity, neutrons determine the isotope; always associate Chadwick with the neutral subatomic particle to avoid confusion with Thomson's cathode ray experiments.