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400
Democritus
Around 400 BC. Democritus believed that matter was made of tiny indivisible particles/spheres which he called atoms.
1.All matter consists of invisible particles called atoms.
2. Atoms are indestructible.
3. Atoms are solid but invisible.
4. Atoms are homogenous.
5. Atoms differ in size, shape, mass, position, and arrangement. http://www.nobeliefs.com/atom.htm
http://the-history-of-the-atom.wikispaces.com/Democritus -
Antoine Lavoisier
In 1774-1777 Antoine Lavoisier performed careful experiments and measurements that led to the Law of Conservation of Matter. He also invented a version of the periodic table with 33 elements. http://en.wikipedia.org/wiki/Antoine_Lavoisier -
Charles Augustin de Coulomb
Inventor/founder of the Coulomb's law. Coulomb's law states that the magnitude of the Electrostatics force of interaction between two point charges is directly proportional to the scalar multiplication of the magnitudes of charges and inversely proportional to the square of the distances between them.
This law helped grasp the concept of electrons and protons making up an atom.
http://en.wikipedia.org/wiki/Coulomb%27s_law -
John Dalton (Atomic Theory)
His three most important postulates were:
1) All matter is composed of tiny, indivisible particles called atoms which cannot be created nor destroyed.
2)Each element atoms that are identical to eachother in all properties which are different from other elements.
3) Chemical reactions are simple rearrangements of atoms from one combination to another in small number ratios.
http://en.wikipedia.org/wiki/John_Dalton -
Johann Wolfgang Dobereiner (Triads)
Döbereiner discovered trends in certain properties of selected groups of elements. For example, the average atomic mass of lithium and potassium was close to the atomic mass of sodium. A similar pattern was found with calcium, strontium, and barium, with sulfur, selenium, and tellurium, and also with chlorine, bromine, and iodine. Moreover, the densities for some of these triads followed a similar pattern. http://en.wikipedia.org/wiki/Johann_Wolfgang_D%C3%B6bereiner -
John Alexander Reina Newlands
Proposed the Law of Octaves 4 years before Mendeleev published his periodic table.
The law states that when elements are placed in the increasing order of atomic masses, the properties of the eight element are repeated. http://www.rsc.org/Education/Teachers/Resources/periodictable/pre16/develop/newlands.htm -
Dimitri Mendeleev
http://atomictimeline.net/index.php
Arranged elements into 7 groups with similar properties. He discovered that the properties of elements "were periodic functions of the their atomic weights". This became known as the Periodic Law. Father of the Periodic Table. -
Lothar Meyer
In 1870, Lothar Meyer, a German chemist, made a chart that plotted atomic volumes against atomic weight. That plot is shown in the picture.
http://dl.clackamas.cc.or.us/ch104-07/lothar_meyer.htm -
Sir William Crookes
He discovered thallium and helium. Used electricity in gases and found as the pressure went down, the electrodes began to emit rays. Discovered cathode rays had the following properties: travel in straight lines from the cathode; cause glass to fluoresce; impart a negative charge to objects they strike; are deflected by electric fields and magnets to suggest a negative charge; cause pinwheels in their path to spin indicating they have mass.
http://atomictimeline.net/index.php -
J.J Thomson
http://atomictimeline.net/index.php
http://www.nobeliefs.com/atom.htm
He discovered electrons and subatomic particles when working with cathode ray tubes. He originally called them corpuscles. He made the Plum(raisin) pudding model shown in the picture. -
Marie Curie (The Curies)
http://the-history-of-the-atom.wikispaces.com/Marie+Curie
http://atomictimeline.net/index.php
http://www.nobeliefs.com/atom.htm
Studied uranium and thorium and called their spontaneous decay process "radioactivity". She and her husband Pierre also discovered the radioactive elements polonium and radium. -
Max Planck
http://atomictimeline.net/index.php
http://www.nobeliefs.com/atom.htm
He was the person who came up with the original quantum theory. To come up with this, he researched previous findings and wrote a book on the quantum theory(the behavior of matter and energy in an atom). Founder of the quanta. Made an equation to support his theory. He also looked at color changes from energy. -
Period: to
Atomic Model Timeline
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Ernest Rutherford
http://www.nobeliefs.com/atom.htm
http://en.wikipedia.org/wiki/Ernest_rutherford
He ionized gas using radiation and found alpha nad beta waves. He discovered the atomic nucleus while he bombarded gold foil with heavy alpha particles and observed deflection of particles. He deduced the nuclear model shown in the picture. -
Neils Bohr
http://www.nobeliefs.com/atom.htm
Neils Bohr concluded that electrons move around the nucleus in circular orbits. Aided by Max Planck'squanta/photons and by using Rutherford's nuclear model, Bohr was able to derive a model of the atom caleed Planetary or solar system model which is shown in the picture. -
Ernest Rutherford
Discovered the basic unit of positive charge in the atom and named it the proton. -
Erwin Schrodinger and Werner Heisenberg
http://www.nobeliefs.com/atom.htm
In 1926, austrian physicist erwin schrodinger wondered why electrons had to be limited to specific orbitals as proposed by neils bohr. He proposed a new model in which electron move in cloudlike orbits rather than fixed ones. He said it is impossible to know the exact location of electrons. The best we can do is know where the electron probably is. He proposed the electron cloud model.Quantum model
At the same time Heisenberg proposed the uncertainty principle. -
James Chadwick
http://atomictimeline.net/index.php
In 1932 James Chadwick discovered a very penetrating form of radiation . He demonstrated that it was the third major particle that makes up the atom and named it "neutron." -
The Quantum Model
From 1932 and on, after the subatomic particles had all been discovered, James Chadwick's model was modified to make the Quantum Mechanic model shown in the picture. from then on, most of the work was focued on nuclear work leading to the discovery of quarks. -
George Zweig and Murray Gell-Mann
In the year my parents were born in Zweig proposed the existence of quarks while a graduate student in physics at the California Institute of Technology in 1964 (independently of Murray Gell-Mann). Zweig dubbed them "aces" after the four playing cards, because he speculated there were four of them. -
My birthday
The Nobel Prize in Chemistry 1995 was awarded jointly to Paul J. Crutzen, Mario J. Molina and F. Sherwood Rowland "for their work in atmospheric chemistry, particularly concerning the formation and decomposition of ozone". Nothing interesting really but I couldn't find any better ones.
