History Electron Proton and Neutron

Before developing the science of chemistry, the Ancient Greek philosophy are familiar with the term atom. According to his view, the atom is the smallest particle of building material. With modern technology, the atoms can be broken down into particles that are smaller, called subatomic particles, ie electrons, protons, and neutrons.

1. Electron discovery

The existence of the electron can be determined based on the cathode ray experiment (Sir William Crookes, 1879). In the experiments, using a device called a Crookes tube or cathode ray tubes called Crookes. If the Crookes tube connected to a high voltage direct current source that will emit a beam cathode towards the anode. The beam called cathode rays. Cathode rays have mass. This can be seen by turning the propeller mounted on the cathode-ray beam path. Observations show that the cathode rays could be deflected by an electric field towards the positive pole of power. It is proved that cathode rays have a negative charge

Based on these facts, what can you conclude? Stoney called cathode rays by electron term. Thus, the electron has a mass and a negative charge. If the cathode material is replaced with another metal cathode rays produced always the same. It is proved that cathode rays or electrons are elementary particles making up matter.

2. Proton discovery

Proved the existence of protons through a modified experimental Crookes tube Crookes tube filled with low-pressure hydrogen gas. This experiment was developed by Eugen Goldstein. If the Crookes tube is connected to the source of electric current in the back of a perforated cathode ray beam will be formed. Goldstein called it as a light beam canal. Therefore canal rays move toward the cathode, we conclude that the canal rays are positively charged. According to Goldstein, the canal rays no other is the hydrogen ion. These ions are formed due to hydrogen gas collide with the cathode rays. Therefore, the hydrogen ion contains only one proton, we conclude that the positive rays are protons. Replacement of hydrogen gas by another gas is always produced by the same rays canal rays generated by hydrogen gas. It can be proved that any material containing protons as one of its constituent particles.

On a modified cathode ray tube, cathode rays ionize the gas in the tube resulting positively charged gas in the tube. Positively charged gas is moving towards the cathode, partly through the gap and mashing cathode tube wall.

3. Neutron findings

The presence of neutrons in the atom was discovered by J. Chadwick through a trial by fire element beryllium high speed alpha particles. From these experiments, formed particles can be influenced by the magnetic field and collide with paraffin. Alpha particles are positively charged particles emitted by radioactive elements.

Experimental data showed that the light coming out of the beryllium targets are not affected by magnetic fields. When the light comes out of the beryllium target of mashing paraffin, paraffin protons will exit at high speed. Chadwick concluded that the particles that come out of the element beryllium was not charged and have a mass similar to the proton mass. Such particles called neutrons.