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The Evolution of the ATOM!
Transcript of The Evolution of the ATOM!
(460 - 370 BC) He called it, "atomos," a Greek word meaning, cannot be divided. He thought there were 4 elements... Aristotle
(384 - 322 BC) He used burning wood to explain his element theory. The fire one was obvious. He said that the air inside the wood was being emitted as smoke and when the wood had turned to ashes, that was representative of the earth Earth Wind FIRE! Water He also felt that no matter how many times you cut a form of matter in half you would end up with a smaller piece of the same matter. The Father of CHEMISTRY! Antoine Lavoisier (1743 – 1794) His discovery that water is made of hydrogen and oxygen! He made many contributions like... His invention of the analytical balance His proposal of the Law of Conservation of Mass His proposal of the Combustion Theory His many contributions led to the inventions and discoveries of others, like... His Law of Multiple Proportions led to the Atomic Theory in 1803 John Dalton (1776-1844) made a system of symbols to represent the atoms of each element, although it is not used today the SI base unit for the amount of a substance Dalton also established the concept of the mole but also that their union formed compounds. He didn't only acknowledged the existence the elements' atoms... made atomic ratios He also used his relative weight scale and from the percent of composition... Joseph John Thom(p)son J. J Thom(p)son
(1856 – 1940) He made many important discoveries like... ELECTRONS (-)!!! His identification of negatively charged particles... ... in the cathode ray tube... a type of analog display device ...in 1897. e/m = -1.76 x 10^8 coulombs/g From this he realized that electrons were a part of all matter. He also developed an equation to find the electron to mass ratio: ...and developed an equation: From the positive rays he discovered that the charge to mass ratio is reliant on the filling gas in the tube... *the largest charge to smallest mass is when hydrogen is the filling gas* e/m = +9.58 x 10^4 coulombs/g. ...known as the plum pudding. He also proposed a model of the atom in which... ...the volume is mostly made of the larger positive portion... The smaller electrons were like the raisins... ...spread throughout the positive mass to keep the charge’s neutrality. Robert Millikan (1868 to 1953) At the University of Chicago in 1909... ... he became known for determining the unit of charge for the electron during an experiment. This enabled the calculation of an electron’s mass and the atoms that are positively charged like so: Because of another experiment in 1911, he proposed the nuclear atom... Ernst Rutherford (1871 – 1937) ... he also proposed that the atom's mass and all of it's positive charge have a small volume in the center of the atom. Its maximum capacity... volume ...being an empty space filled with electrons. When he put all that together he came up with an atomic structure. Also in 1911 Rutherford published the results of his gold foil experiment He used a screen that was coated with zinc sulfide... ...which emitted a flash of light when a particle hit it. NEXT! NEXT! Rutherford (along with his assistant Hans Geiger)... sat in the dark until their eyes were sensitive enough to try and count the flashes of light reflected off the zinc sulfide screen In 1920, Ernst Rutherford was the first to call the hydrogen nucleus a proton! The first to suggest the existence of the neutron! In his day, these ideas were viewed as very radical. NEXT! Henry Moseley (1887 – 1915) He discovered an increasing linear pattern in the emission of energy from x-rays by elements along with the sequence of the elements on the periodic table. Moseley suggested there was a relationship with the function of the positive charge of the nucleus in 1913... ...this rearranged the periodic table because it replaced the method of using atomic mass to represent the progress of the elements with the use of the atomic number. NEXT! Niels Bohr (1885 - 1962) which could be defined by their angular momentum ... He applied the quantum theory to the atomic structure created by Ernst Rutherford. From this a calculation of the orbits' possible energy levels was developed... ... then the theory that electrons moving into the lower energy orbit causes light emissions. His equation of 2n^2 and his atomic model are still useful in chemistry today. NEXT! James Chadwick (1891 – 1974) Although Rutherford proposed the existence of the neutron, in 1932 he discovered it! He repeatedly noticed that the number of protons in the nucleus the atomic number ...was less than the average mass of the atom the atomic mass Electrons have very little mass... almost none ...so Chadwick knew that there had to be something other than protons adding to the mass. To try and solve this problem... ...he repeated Europeans experiments... (especially those of Frederic and Irene Joliot – Curie) ...because they used a different method of tracking the radiation of particles. He was able to find a neutral particle that had the same mass as a proton but a charge of zero ... ...and determine the actual existence of the neutron mass of 0.1% more than the proton’s (Antoine) Henri Becquerel (1852-1908) In 1896, he discovered mysterious radiation (along with Marie and Pierre Curie)... while conducting an experiment involving the exposure of uranium- bearing crystal to sunlight This lead to his theory that absorbed energy from the sun was released in the form of x-rays by the uranium. was named after Marie’s native country of Poland Marie Curie
(1867-1934) Pierre Curie
(1859-1906) They are famous for their trailblazing work in radioactive studies and made many scientific advances and discoveries. Along with Henri Becquerel, they won the Nobel Prize (for physics in 1903) because of their discovery of radioactivity in 1896. During their own experiments, they came up with the term “radioactivity” while testing uranium-containing ore. In a comparison of that substance and pure uranium, they found that the uranium- containing ore had more radioactivity that the pure element... ...this gave them the conclusion that ore had more radioactive components than just uranium. As a result of those experiments and observations in 1898 they discovered the elements, radium and polonium [his Quantum Theory] Max Planck
(1858-1947) NEXT! In 1900 he discovered that the WSM... Wave Structure of Matter ...and the Standing Wave Interactions ... occurring only at Discrete Frequencies explaining the Discrete Energy Exchanges of l=Light ...explain the Quantum Energy States of Matter and Light Quanta (E=hf) NEXT! In 1913, he assumed electrons traveled in stationary orbits... N E X T! This provided useful inferences of what can be measured at the atomic level. Werner Heisenberg
(1901-1976) Before his discovery it was assumed that it was always possible to find the exact location and velocity. But Heisenberg found that at the atomic level this was not possible because the act of observation affected the location... ...and velocity of smaller particles like the electron. This happens because observation needs light... ...and when the light bounces off the electron... ... the exchange of momentum causes the location and velocity to be changed. In 1923 he explained the “Uncertainty Principle.” The size, shape and positioning in space of the orbitals on the atom are described by those quantum numbers (coordinates).
Erwin Schrödinger (1887 – 1961) NEXT! He developed a very useful atom model in 1926, after combining equations involving the behavior of waves with the “de Broglie” equation... First equation: KE = (1/2) mv^2 ...giving him a mathematical model depicting the distribution of an atom’s electrons. These mathematical equations are known as wave functions that followed the necessities of an electrons behavior. Second equation: λ = h/p But, the actual physical model of the waves of the electrons is hard to imagine. Schrödinger’s model also described the probability of where the electron could be instead of actually telling you where it is. Also in his model, the electron was able to occupy three dimensional space, instead of one dimensional. This model needed three quantum number [coordinates that tell you where the electron could be] : The principal (n)
The angular (l)
The magnet (m) NEXT! e = 1.60 x 10^-19 coulombs ~THE END~