Who discovered the nucleus? Describe the experiment that led to this discovery.

The nucleus was discovered by Ernest Rutherford, a New Zealand-born British physicist, in 1911.

The experiment conducted by Ernest Rutherford, which ultimately led to the discovery of the nucleus, is known as the gold foil experiment, or the Rutherford's alpha particle scattering experiment. In this experiment, Rutherford and his assistants attempted to understand the structure of an atom by observing the behavior of alpha particles as they passed through a thin gold foil.

Rutherford and his team set up the experiment by placing a radioactive substance (which emitted alpha particles) in a lead box. A tiny hole in the box allowed the alpha particles to exit in a straight line. These alpha particles then moved towards a thin gold foil, which was surrounded by a circular fluorescent screen. The screen would light up when struck by the alpha particles, helping the researchers to trace the particles' trajectory.

As the alpha particles passed through the gold foil, Rutherford and his team observed their behavior on the fluorescent screen. They expected most of the alpha particles to pass straight through the foil with little or no deflection, based on the previous atomic model (Thomson's plum pudding model), which suggested that the positive charge within an atom was evenly distributed throughout its volume.

Rutherford and his team were surprised to find that while most alpha particles did indeed pass straight through the gold foil, a small portion of them were deflected at various angles. Some alpha particles even bounced back towards the source, as if they had encountered a strong repulsive force within the gold atoms. This observation was inconsistent with Thomson's plum pudding model and indicated the presence of a concentrated positive charge within the atom.

Based on the experimental results, Rutherford proposed a new atomic model that included a central positive charge, which he called the nucleus. According to Rutherford's nuclear model, the positive charge (protons) and most of the atom's mass were concentrated in a small central region (the nucleus), while the electrons were dispersed in the surrounding space. This model explained the observed deflection and backscattering of alpha particles as they interacted with the concentrated positive charge of the nucleus. In conclusion, Ernest Rutherford discovered the nucleus and proposed a new atomic model through his groundbreaking gold foil experiment. This experiment challenged the previously accepted understanding of atomic structure and laid the foundation for modern atomic theory.