1900-Present

=__ **Atomic Theory: 1900-Present** __=


 * Niels Bohr ||  || [[image:reich-chemistry:NielsBohr1.jpg width="238" height="326" caption="Niels Bohr 1865-1962"]] ||

1865-1962 Bohr published a theory about the structure of the atom based on an earlier theory of Rutherford's. Bohr expanded upon this theory by proposing that electrons travel only in certain larger orbits. He suggested that the outer orbits could hold more electrons than the inner ones, and that these outer orbits determine the atom's chemical properties. For his research he received the Nobel Prize in physics in 1922.


 * Marie Curie ||  || [[image:reich-chemistry:mariecurie_2.jpg width="235" height="360" caption="Marie Curie"]] ||

1867-1934 Curie studied uranium radiations. She found that the radiations from the ore were more intense than those from uranium she realized that unknown elements were even more radioactive than uranium were present. Marie Curie was the first to use the term 'radioactive' to describe elements that give off radiations as their nuclei break down. Marie Curie was the first female recipient of the Nobel Prize.


 * Robert Millikan ||  || [[image:reich-chemistry:millikan.jpg width="235" height="327" caption="Robert Millikan"]] ||

1868-1953 In 1909 Millikan began a series of experiments to determine the electric charge carried by a single electron. He began by measuring the course of charged water droplets in an electrical field. The results suggested that the charge on the droplets is an electric charge, but the experiment was not accurate enough to be convincing. He obtained more precise results in 1910 with his famous oil-drop experiment in which he replaced water with oil.

Rutherford ||  ||  ||
 * Ernest

1871-1937 He discovered alpha and beta rays, which set forth the laws of radioactive decay, and identified alpha particles as helium nuclei. Most importantly he discovered the nuclear structure of the atom by observing experiments done in Rutherford's laboratory which showed that when alpha particles are fired into gas atoms, a few are violently deflected. He also discovered half-life of radioactive elements.



Chedwick ||  ||  ||
 * James

1891-1974 He made a fundamental discovery in the domain of nuclear science where he proved the existence of neutrons. Chadwick's discovery was advanced experimental work for all scientists, and in his experiments since neutrons have no electrical charge, any neutrons fired from a source has the ability to go through deep layers of materials.

1878-1968 Was the first to articulate a theory of how the nucleus of an atom could be split by the ejection of neutrons with high amounts of energy and established why no elements beyond uranium existed naturally, as the expulsion by protons would be too strong.
 * Lise Meitner ||  || [[image:index.jpg width="213" height="330"]] ||

Heisenberg ||  ||  ||
 * Werner

1901-1976 He found out that you could measure the position of an electron or you could measure its momentum, but the more precisely you measure one property, the more you throw the other off. He used this information to make an equation using Planck's constant, and called it the uncertainty principle.

Schrodinger ||  ||  ||
 * Erwin

1887-1961 He was an Austrian physicist who invented wave mechanics in 1926. Wave mechanics are the mathematically described behavior of electrons and atoms.