question is below wouldnt all fit in the question below!?

Question

What observations by Rutherford led to the hypothesis that atoms are mostly empty space, and that almost all of the mass of the atom is contained in an atomic nucleus?

Answer 1

The Rutherford model of the atom was devised by Ernest Rutherford. He performed his famous Geiger-Marsden experiment (1909), which showed that the Plum pudding model ( of J. J. Thomson) of the atom was incorrect. In the experiment, Rutherford allowed alpha particles to pass through a thin piece of gold foil. He predicted that most of the particles would pass through the foil or be deflected slightly. This is what happened most of the time, but a few particles, 1 in 8000, bounced back towards the source. This directly supported the hypothesis that atoms have a dense region containing most of their mass, associated with a highly concentrated electric field (probably positive in nature), instead of spread-out positive or negative field. Rutherford thought it likely, on purely symmetric and aesthetic grounds, that such a region of dense charge and mass, would be located in the atom's core, or center.

In 1911, Rutherford came forth with his own physical model. In it, the atom is made up of an atomic nucleus surrounded by a cloud of orbiting electrons. In this 1911 paper, Rutherford only commits himself to a region of very high positive or negative charge in the atom, but uses this language for pictorial purposes: "For concreteness, consider the passage of a high speed a particle through an atom having a positive central charge N e, and surrounded by a compensating charge of N electrons." However, the Rutherford model did not attribute any structure to the orbits of the electrons themselves, though it did mention atomic model of Hantaro Nagaoka, in which the electrons are arranged in a ring (this is the ONLY previous atomic model mentioned in the 1911 paper).

The Rutherford model of the atom was soon superseded by the Bohr atom, which used some of the early quantum mechanical results to give locational structure to the behavior of the orbiting electrons, confining them to certain circular (and later eliptical) planar orbits. Since the Bohr model is an improvement on the Rutherford model, some sources combine the two, referring to the Bohr model as the Rutherford-Bohr model.

The Rutherford model was important because it essentially proposed the concept of the nucleus, although this word is not used in the paper. What Rutherford notes as the (probable) concomitant of this results, is a "concentrated central charge" in the atom: "Considering the evidence as a whole, it seems simplest to suppose that the atom contains a central charge distributed through a very small volume, and that the large single deflexions are due to the central charge as a whole, and not to its constituents." The central charge containing most of the atom's positive charge, invariably later become associated with a concrete structure, the atomic nucleus.

After the Rutherford model and its confirmation in the experiments of Henry Moseley and its theoretical description in the Bohr model of the atom, the study of the atom branched into two separate fields, nuclear physics, which studies the nucleus of the atom, and atomic physics which studies atom's electronic structure.