What significant component did Rutherford discover in the nucleus of an atom?

Rutherford's significant discovery in the nucleus of an atom was the existence of protons. Through his famous gold foil experiment, Rutherford demonstrated that atoms contain a dense and positively charged nucleus at their center, which occupies a very small volume compared to the overall size of the atom. This nucleus contains most of the atom's mass and is positively charged, explaining why alpha particles were deflected at large angles when they hit the foil.

The identification of protons as the primary positive charge carriers in the nucleus was crucial in understanding atomic structure. Protons have a positive charge equal in magnitude but opposite in sign to that of electrons, which orbit the nucleus. This balance between the positive charge of the protons and the negative charge of the electrons is fundamental to the stability of atoms and the formation of chemical bonds.

In understanding the correct answer, it's clear that while neutrons, electrons, and quarks are important components of atomic structure, Rutherford specifically focused on the proton and its role within the nucleus during his seminal experiments. Neutrons, for instance, were discovered later, and quarks are fundamental particles that make up protons and neutrons but were not identified until much later in particle physics.