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460
Aristotle
Thought the atomic idea was worthless, people respect the thinking of Aristotle and they also dismissed the idea od atomic structure. This thought didnt inhance the atom, it was telling people it didnt exsist and dismissed the idea. -
460
Democritus
Developed first thought of the atom. Asked the question: If you break a piece of matter in half, and in half again how long until it will break no more? With this question he thought it would stop at some point, and called these basic particles atoms. -
Period: 460 to
atom advances
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Antoine Lavoisier
Antoine is called the father of modern day chemistry, since he discovered/invented many things used in basic chemistry. One thing he discovered was that water is made up of hydrogen and water, He invented the analytical balance and showed that chemical elements were neither created nor destroyed, just combined into different compounds in chemical reactions. And from this came one of the most important baisc things in physics-the consevation of mass. -
John Dalton
In the 1800's he performed various experiments with various chemicals that showed that matter indeed did consist of elementary lumpy particles or atoms. Yet he knew nothing about their structure he knew it was evidence pointing to something fundamental. This changed the perpesctive again saying there was tiny matter inside everything. -
Henri Becquerel
he was the son of the physicist Alexandre-Edmond Becquerel. Becquerel's early work focused on plane-polarized light, the phenomenon of phosphorescence (in which certain compounds glow after being exposed to direct light). But all of his early research became overshadowed by his discovery of natural radioactivity. Although Becquerel did not initially comprehend what he was observing, his landmark discovery of radioactivity paved the way for a new understanding of the atom. -
J.J. Thomson
Thomson thinking inhanced the atom by saying there were other things in the atom. So he discovered the electron. He knew they had a negative charge and concluded that atoms or matter had a positive charge, his model was called the "plum pudding model". Since it looked like lumps on pudding. -
marie and pierre curie
Wife of pierre first and then henri becquerel, marie is best known for her joint pioneering work in the study of radioactivity, which led to her and pierre's discovery in 1898 of the elements radium and polonium. -
Max Planck
His theroy was that if you vibrated the atoms fast or strong enough, like when you heat something till it glows, you can measure the energy in discrete amounts, which he called quanta. This thoery was called the quantam theory. This advanced the thinking in the atom because it showed there was an even smaller part to the smallest know thing in matter. Yet albert einstein said the discrete particles were not waves as physicists thought but indeed discrete particles, and then called it a photon. -
Pierre Curie
he distinguished himself in the study of the properties of crystals. He discovered the phenomenon of piezoelectricity, whereby changes in the volume of certain crystals excite small electric potentials. Along with work on crystal symmetry, Pierre Curie studied the magnetic properties of materials and constructed a torsion balance with a tolerance of 0.01 mg. He discovered that the magnetic susceptibility of paramagnetic materials is inversely proportional to the absolute temperature. -
robert millikan
As a result of j.j. thomson's findings on how to measure the charge to mass ratio of the electron, millikan did an ecperiment called the "oil-drop experiment" and it was the first successful scientific attempt to detect and measure the effect of an individual subatomic particle. He used this formula to measure the charge on a drop in the experiment: m · g = q · E -
Ernest Rutherford
Rutherford thought to bombard the atoms with alpha rays, figuring that this would help investiagte the inside of the atoms, like a probe. He used Radium as the source of the alpha particles and shinned them onto the atoms in gold foil. The results of the experiments came unexpected. Most of the alpha particles went smoothly through the foil. Only an occasional alpha veered sharply from its original path. -
Ernest Rutherford cont.
Sometimes bouncing straight back from the foil! Rutherford reasoned that they must get scattered by tiny bits of positively charged matter. Most of the space around these positive centers had nothing in them. He thought that the electrons must exist somewhere within this empty space. Rutherford thought that the negative electrons orbited a positive center in a manner like the solar system where the planets orbit the sun. This again advancede the thinking about the atom and its smaller inside. -
Rutherford cont
Rutherford knew that atoms consist of a compact positively charged nucleus, around which circulate negative electrons at a relatively large distance. The nucleus occupies less than one thousand million millionth (10 ) of the atomic volume, but contains almost all of the atom's mass. If an atom had the size of the earth, the nucleus would have the size of a football stadium. -
Neil Bohr
The theory of electricity and magnetism predicted that opposite charges attract each other and the electrons should gradually lose energy and spiral inward. Moreover, physicists reasoned that the atoms should give off a rainbow of colors as they do so. But no experiment could verify this rainbow. Niels Bohr came up with a theory that said the electrons do not spiral into the nucleus and came up with some rules for what does happen. These rules were: -
niel bohr cont.
These rules included:
Electrons can orbit only at certain allowed distances from the nucleus.
Atoms radiate energy when an electron jumps from a higher-energy orbit to a lower-energy orbit. Also, an atom absorbs energy when an electron gets boosted from a low-energy orbit to a high-energy orbit. -
Henry Moseley
He studied under Rutherford. With the discovery of isotopes of the elements, it became apparent that atomic weight was not the significant player in the periodic law as Mendeleev, Meyers and others had proposed, but rather, the properties of the elements varied periodically with atomic number. When atoms were arranged according to increasing atomic number. Because of Moseley's work, the modern periodic table is based on the atomic numbers of the elements. -
Rutherford
Rutherford finally identify the particles of the nucleus as discrete positive charges of matter. Using alpha particles as bullets, Rutherford knocked hydrogen nuclei out of atoms of six elements: boron, fluorine, sodium, aluminum, phosphorus, an nitrogen. He named them protons, from the Greek for 'first', for they consisted of the first identified building blocks of the nuclei of all elements. He found the protons mass at 1,836 times as great as the mass of the electron. -
Werner Heisenberg
Werner Heisenberg, in 1925, had a theory of his own called matrix mechanics which also explained the behavior of atoms. The two theories seemed to have an entirely different sets of assumptions yet they both worked. Heisenberg based his theory on mathematical quantities called matrices that fit with the conception of electrons as particles whereas Schrödinger based his theory on waves. Actually, the results of both theories appeared mathematically the same. -
Erwin Schrodinger
Why not go all the way with particle waves and try to form a model of the atom on that basis? His theory worked kind of like harmonic theory for a violin string except that the vibrations traveled in circles.The world of the atom, indeed, began to appear very strange. It proved difficult to form an accurate picture of an atom because nothing in our world really compares with it. Schrödinger's wave mechanics did not question the makeup of the waves but he had to call it something, so made symbol. -
Werner Heisenberg
Heisenberg formulated an idea, which agreed with tests, that no experiment can measure the position and momentum of a quantum particle simultaneously. Scientists call this the "Heisenberg uncertainty principle." This implies that as one measures the certainty of the position of a particle, the uncertainty in the momentum gets correspondingly larger. The visual concept of the atom now appeared as an electron "cloud" which surrounds a nucleus. -
James Chadwick
James Chadwick finally discover the neutron. He found it to measure slightly heavier than the proton with a mass of 1840 electrons and with no charge (neutral). The proton-neutron together, received the name, "nucleon." Although scientists knew that atoms of a particular element have the same number of protons, they discovered that some of these atoms have slightly different masses. They concluded that the variations in mass result (determined by nuetrons) were to be called isotopes.
