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Dalton's Atomic Theory
Attempting to explain how and why elements combine John Dalton formulated his Atomic Theory. It is composed of five points: 1) All matter is made of Atoms. 2) They cannot be made, and are inextinguishable. 3) All Atoms of the same element are similar. 4) Different elements have different types of Atoms. 5) Chemical reactions take place when Atoms are changed. Even though some of his points are now spoken as incorrect, he created a basis for new experiments, and his theory propelled new ones. -
The Curies Discover Radioactivity
Antoine Becquerel conducted an experiment, and discovered radioactivity but did not examine it. Husband and wife Pierre and Marie Curie later became interested in finding out more about this discovery. Through their own experimentation with pure uranium, and uranium ore (which are minerals from which uranium can be taken), they understood that certain elements naturally discharge radiation more than others. They came to terms with this and called it radioactivity. -
Joseph John Thomson Discovers the Electron
J.J. Thomson's atomic theory focused on the chemical side. Stating that the atom was a sphere like structure which involved the "electron". He conducted a series of designed experiments to reach this conclusion. He used high-vacuum cathode-ray tubes to study the nature of atoms electric discharges. One of his last experiments focused on discovering the nature of positively charged particles; through this he established the idea of isotopes in nonradioactive elements, through mass spectrograph. -
Robert Millikan and the Electron
In 1909 Millikan began conducted a series of experiments that was aiming to study the electrical charges of the electron. His experiment was known as the Millikan oil-drop experiment. Basically, what he did was spray pre-charged drops of oil every minute on a built chamber, and then calculating the gravitational force in order to determine the electric charge before, and after. By this he was able to discover the charge on each single electron. -
Neil Bohr's Theory
In the year 1913 Neil Bohr established his own theory that described the atom as a model with electrons that revolve around a nucleus. Through extensive research he came to terms with his findings by combining works from Ernest Rutherford, and the Planck’s Quantum Theory. His theory simply explained the atomic structure and clarified why it was limited in size. -
Irving Langmuir's Theories
In 1915 Irving Langmuir named atoms that could share electron pairs with other atoms; covalent. In 1919 Langmuir's concentric theory of the atomic structure
(which details that chemical forces have boundaries between different substances) built on a previous cubical atom theory, and chemical bonding theory. His theory discussed the chemical forces between different substances. -
Ernest Rutherford Discovers Protons and Neutrons
In 1918 Ernest Rutherford formulated his theory, stating that the atom had positive charged particles; which he named Protons. He also introduced that there was neutral particles that were in the atoms nucleus; which he later named Neutrons. Rutherford came to this conclusion through conducting his well-known "gold foil" experiment. In this experiment he used thin gold metal foils and he directed radioactive particles at them. He detected them by using zinc sulfide coated screens. -
Louis de Broglie's Particle Wave
De Broglie proposed an idea that clarified how electrons acted like waves in some conditions. Instead of his idea being experimental, it was theoretical and based on math. His proposal showed other scientists that the atom was not in fact like a solar system, because it did not have a regular orbit. His theory helped describe and clarify the behavior of an atom. -
Paul Dirac
Paul Dirac focused an fields regarding the atomic theory and structure. He designed a different form of quantum physics that determined the motion of atomic particles. Dirac suggested that the electrons could not be described in wave functions because its placement was still irresolute. Therefore he came to terms that an electron must rotate around the nucleus on its axis. -
Erwin Schrodinger's Quantum Physics
Through utilizing wave equations Schrodinger was able to find out the energy states of matter of particles. By formulating physics equations he found out that frequency and wavelength could be put into wave equations to express energy and momentum. Therefore reflecting on the energy of electrons. -
Werner Heisenberg's Uncertainty Principle
In 1927 Heisenberg proposed the idea of imprecision in science. He stated that exact values could not be obtained in certain pairs, due to limitations of measurement. This was used to prove how it is not possible to know where a particle is at an exact given time. Because when one magnitude of a particle is measured (velocity, mass, or position) then the rest become a blur; this is due to the fundamental property of nature. -
James Chadwick Proves the Neutron's Existence
In the year 1932 Chadwick conducted many tests to try to sort out the deal behind this particle. The test he conducted was based on a piece of Beryllium bombarded with alpha particles. This pair created a strange radiation and Chadwick began putting the pieces together. He concluded that there was a neutral particle in the atom, and he therefore substantiated Rutherford’s theory. -
Murray Gell-Mann and George Zweig's Atomic Theory
The two men wanted to simplify the confusing picture of hadrons "the family of particles that feel the strong nuclear force and includes protons and neutrons". They did this by putting hadrons into tables, and creating a characterization setting. They named the particles that make up a hadron "quarks", and suggested that the arrangement of quarks has an affect on the different properties within a hadron. Properties like how the atoms insides spin, and the pattern it withholds.
