-
354
Aristotle
-Believed of the four elements: air, water, earth, fire
-Rejecte Democritus' ideas
-Thought that you will always have a smaller piece of atom matter source
http://cstl-csm.semo.edu/cwmcgowan/ch181/atomhist.htm -
400
Democritus
-used the word "atomos" for atom
-father of the atom
-believed all things consisted of tiny indivisual units source
atomic theory notes slide 2 -
Robert Boyle
-Reintroduced the idea of the atom
-Displaced the ideas by Aristotle
-Called groups of atoms bodies
-Supposed elements were ultimately composed of particles of various sorts and sizes, into which, they were not to be relsolved in any known way source
http://www.crystalinks.com/boyle.html -
Isaac Newton
-Proposed a mechanical universe with small solid masses in motion
-Began to understand that atoms and or particles move and are not stationary source
http://atomictimeline.net/index.php -
Antoine Lavoisier
-Proposed combustion theory (based on sound mass measurements)
-Named Oxygen source
http://cstl-csm.semo.edu/cwmcgowan/ch181/atomhist.htm -
John Dalton
-Developd first atomic theory
-Billiard Ball Model: each atom had a certain mass, size, and chemical behavior determined by element kind
-Element consisted of atoms, all atoms of an element are identicle, each element is different (mass), chemical reaction involved the rearrangement of atoms source
atomic structure notes slide 3-8 -
Joseph Gay-Lussac
-Anouncd law of combining volumes
-Showed that at thew same temperature and pressure two volumes of hydrogengas reacted with one volume of oxygen gas to produce two volumes of water sources
http://cstl-csm.semo.edu/cwmcgowan/ch181/atomhist.htm -
Amadeo Avogadro
-Proposed molecular theory; two assumptions:
1..Avogadro hypothesis- equal volume of gasses contains equal nuber of moecules at the same temperature and preassure
2..gas molecules can divide during chemical reactions
-Based on speculative assumptions
-Lacked independent experimental evidence or theoretical evidence source
http://www.chemistryexplained.com/Ar-Bo/Avogadro-Amedeo.html -
Michael Faraday
-Discovered the relationship between electricity and magnetism (one could not exist without the other)
-felt light was the motion or vibration of these lines of force source
http://www.writework.com/essay/history-atomic-theory-and-michael-farraday-including-his-d -
J. Plucker
-built first functioning Cathode Ray
-theorized that atomic particles contain a charge source
http://www.preceden.com/timelines/65160-atomic-theory-timeline-project -
Dimitri Mendeleev
-Developed first periodic table
-Arranged by chamical properties
-Listed elements in columns of increasing atomic mass, had many blank spaces for new elements Source
http://cstl-csm.semo.edu/cwmcgowan/ch181/atomhist.htm
http://creating.pbworks.com/w/page/16595568/Mendeleev%20and%20the%20periodic%20table -
JJ Thomson
-Discovered electron using Cathode Ray Tube
-tested several experiments each result was the same
-Plum pudding model: most popular and widely accpted in that timw, atom had an internal structure source
atomic structure notes slide 9-13 -
Marie Curie
-discovered radioactive elements Polonium and Radium
-studied uranium and thorium
-called her spontaneous decay process "radioactivity" Sources
http://atomictimeline.net/index.php -
Phllip Lenard
-correctly concluded that the majority of an atomsvolume is empty space
-His model was composed of Dynamids: could account for atomic masses, internal structure, and the emptiness in the atom
-Used the Aluminum Experiment-beam of electrons could pass
through a sheet of Al foil source
atomic structure notes slide 19-22 -
Hantaro Nagaoka
-first to present the atomic model close to the present day model
-His model: was unstable and according to laws of planetary motion the atom will collapse over time, explained electrons moving around nucleus
-atoms were able to give off electrons to form ions source
atomic structure notes slide 23-26
-explained different atomic weights -
Richard Abegg
-Concluded that noble gasses are stable because of the 8 electrons in the outermost shel
-proposed the valence bond theory
-found that inert gasses have a stable "electron configuration" Sourse
http://www.msnucleus.org/membership/html/jh/physical/atomictheory/lesson3/atomic3c.html
http://www.barcodesinc.com/articles/timeline-on-atomic-structure.htm -
Albert Einstein
-The quanta behaved like discrete particles which are called photon
-atoms emit and absorb them
-Albert wrote a paper that explained that light absorbtion can release electrons from atoms called "photoelectric effect" source
http://www.nobeliefs.com/atom.htm -
Robert Millikan
-Determined unit charge of electron with oil drop experiment
-electron= 1.60 x 10^-19
-Allowing for calculation of mass source
http://creating.pbworks.com/w/page/16595568/Mendeleev%20and%20the%20periodic%20table -
Ernest Rutherford
-Gold foil Experiement: proved atoms had a tiny, positivly charge center and atoms were mostly empty space
-Discovered the nucleus
-Nucleaus takes up majority of the atoms mass
-Electrons move around the empty space surrounding nucleus source
atomic structure notes slide 14-18
atomic structure notes slide 14-18 -
Fredrick Soddy
-proposed that the same element exists in different forms
-Theory of isotopes: different elements can be chemically indistinguishable but have different atomic weights
-demonstrated how radioactive elements can disenigrate Source
http://www.nndb.com/people/286/000099986/ -
Bohr
-Student of Rutherford
-electrons are placed in energy levels surrounding the nucleus
-most extensive
-explained how electrons could give off light source
atomic structure notes slide 27-29 -
HGJ Mosely
-discovered systematic relation between wavelength and atomic number
-sorted chemical elements by their atomic number
-developed early x-ray spectrometry equipement source
http://www.famousscientists.org/henry-moseley/ -
Francis Anston
-Invented mass spectograph
-first to observe isotopes (three different hydrogen atoms) Source
http://cstl-csm.semo.edu/cwmcgowan/ch181/atomhist.htm -
Louis de Broglie
-suggested electrons could act as both particles and waves
-hypothesis confirmed in experimentthat showed electron beams could be diffracted or bent as they pass through a slit -
Werner Heisenberg
-Heisenberg uncertainty principle: it is impossoble to know exactly both the velocity and position of a particle at the same time
-we shouldn't view electrons as moving in well-defined orbits around the nucleus source
http://www.howstuffworks.com/atom8.htm source
http://www.howstuffworks.com/atom8.htm -
Erwin Schrodinger
-derived a set of wave functions for electrons
-orbitals could be described as density clouds
-densest area= greatest chance of finding an electron
-least dense= lowest chance of finding an electron Source
http://www.howstuffworks.com/atom8.htm -
Paul Dirac
-predicted the existence of antiparticles and known for quantum mechanics
-formulated quantum field theory Source
http://www.famousscientists.org/paul-dirac/ -
James Chadwick
-discovered neutron
-nuclear fission of Beryllium and beta radiation released a neutron Source
atomic structure notes slide 31 -
Glenn Seaborg
-discovered transuranium elements (6)
-him and colleagues are responsible for the identification of more than 100 isotopes throughtout the periodic table
-suggested a change om the layour of the periodic table Source
http://www.nobelprize.org/nobel_prizes/chemistry/laureates/1951/seaborg-bio.html -
Enrico Fermi
-demonstrated that nuclear transformation occurs in almost every element subjected to neutron bombardment
-conducted first controlled chain reaction releasing energy from the atom's nucleus source
http://atomictimeline.net/index.php
