Which hypothesis led to the discovery of the proton

A person knowledgeable about cars would include more details, but everyone would have the basic information in their description. What makes the description easy to come up with?

We can see it, we have a common language to describe it size, color, construction , and we have a basic idea of what it is a car, not a house or a tree. Scientists have far more difficulty in describing things they cannot see.

There is no way to look directly at an atom and see its detailed structure. When a discovery is first made, there is often no language to use to tell others exactly what it is. This was the problem in talking about the atom and its structure.

Research builds upon itself—one piece connects to another. Each finding gives a clearer picture of the whole and also raises new questions. The detective work that led to the discovery of the proton was built upon finding pieces to the puzzle and putting them together in the right way.

The electron was discovered using a cathode ray tube. An electric current was passed from the cathode the negative pole to the anode positive pole. Several experiments showed that particles were emitted at the cathode and that these particles had a negative charge. These experiments demonstrated the presence of electrons. If cathode rays are electrons that are given off by the metal atoms of the cathode, then what remains of the atoms that have lost those electrons?

An experimental breakthrough came in with the observation by the German nuclear physicist Herbert Becker and Walther Bothe that bombardment of beryllium with alpha particles from a radioactive source produced neutral radiation which was penetrating but non-ionizing. They observed that the penetrating radiation was unaffected by electric fields and hence, they assumed it to be gamma radiation. In the year , Frederic Joliot-Curie and Irene Joliot-Curie demonstrated that these rays have the potential to eject protons when it strikes paraffin or any H-containing compounds.

The experiment proved that the assumption that the rays to be gamma rays was wrong. Because a photon that does not have mass cannot be capable to release a particle times heavier than an electron protons. Therefore, it was concluded that the ejected rays cannot be photons. Neutron was discovered by Sir James Chadwick in He performed the same experiment performed by Frederic Joliot-Curie and Irene Joliot-Curie and used different bombardment targets other than paraffin.

He fired alpha radiation at the beryllium sheet from a polonium source. This led to the production of an uncharged, penetrating radiation. These radiations were made incident on paraffin wax, having relatively high hydrogen content. The range of the liberated protons was measured and the interaction between the uncharged radiation and the atoms of several gases was studied by Chadwick.

The particle ejected was found to have a mass equal to that at proton and no charge. He called these particles as neutrons. Characteristics of Neutrons:. Let us investigate the discovery of protons through detailed explanation of the Canal Ray Experiment performed by Goldstein. Goldstein used almost the same discharge tube as the cathode ray discharge tube used for discovery of electrons.

Apparatus - Canal ray experiment apparatus consists of a tube known as anode rays discharge tube which is made of glass containing two thin pieces of metal, called electrodes, sealed in it. Out of these two electrodes one electrode or one metal piece has many holes in it which acts as a cathode while another electrode acts as anode. Both the electrodes are connected to the high voltage generator. The electrical discharge through the gases could be observed only at very low pressures and at very high voltages.

So, the tube was evacuated so that pressure of different gases could be adjusted. When sufficiently high voltage is applied across the electrodes, current start flowing through a stream of particles in the tube. Procedure and observation — Electric current was passed through both the electrodes which creates an electric field in the tube and ionizes the gaseous atoms in the tube. At this point anode starts emitting positively charged rays which move towards the negatively charged cathode and passes the holes of the cathode and strike the glass walls of the tube at the end near the cathode.

These rays produced a faint red glow. These rays were passing in the opposite direction of the cathode rays so it was concluded that the charge they carry must be opposite of cathode rays. As these rays were moving from anode to cathode so called anode rays as well. Due to the same reason the glass tube used in this experiment was called anode rays discharge tube. The characteristics of positively charged particles of canal rays are listed below —. Unlike cathode rays, mass of positively charged particles depends upon the nature of gas present in the anode ray tube.