《Atomic Theories Timeline：原子理论的时间表》由会员分享，可在线阅读，更多相关《Atomic Theories Timeline：原子理论的时间表（31页珍藏版）》请在金锄头文库上搜索。
1、Atomic TheoryLets Take a Trip Through Time!Democritus 460 370 B.C. There are various basic elements from which all matter is made Everything is composed of small atoms moving in a void Some atoms are round, pointy, oily, have hooks, etc. to account for their properties Ideas rejected by leading phil
2、osophers because void = no existenceFirst Concept of an AtomJohn Dalton 1766-1844Each element is composed of extremely small particles called atoms All the atoms of a given element are identical, but they differ from those of any other element Atoms are neither created nor destroyed in any chemical
3、reaction A given compound always has the same relative numbers and kinds of atoms6Daltons Atomic Theory (1808)1. Elements are composed of extremely small particles called atoms. 2. All atoms of a given element are identical, having the same size, mass and chemical properties. The atoms of one elemen
4、t are different from the atoms of all other elements.3. Compounds are composed of atoms of more than one element. In any compound, the ratio of the numbers of atoms of any two of the elements present is either an integer or a simple fraction (Law of Definite Proportion).4. A chemical reaction involv
5、es only the separation, combination, or rearrangement of atoms; it does not result in their creation or destruction.Daltons Model8Law of Multiple Proportions98 X2Y16 X8 Y+Law of Conservation of MassModern Atomic Theory “Atoms cannot be subdivided, created, or destroyed.” Atoms can be destroyed via n
6、uclear reactions but not by chemical reactions. “Atoms of a given element are identical* in size, mass, and other properties;” There are different kinds of atoms (differing by their masses) within an element that are known as “isotopes“. J.J. Thomson(Discovery of Electron) 1856-1940 Discovered elect
7、ron 1897 Cathode Ray Experiment Plum Pudding model 1904 Electrons in a soup of positive charges Discovered isotopes 1913 J. J. Thomson(1897) British physicist at Cambridge University Cathode Ray Experiment Hypotheses Cathode rays are charged particles (which he called “corpuscles“). These corpuscles
8、 are constituents of the atom. Observation: -the rays bended with a magnet -the electrometer measured a large amount of negative charge Discovery of Electron13J.J. Thomson, measured mass/charge of e- (1906 Nobel Prize in Physics)Cathode Ray TubeThe Electron J.J. Thomson 1897 - CRT experiment Negativ
9、e Charge e- Actual Mass: 9.11 x 10-28g Relative mass information - discovered later 1/1840 the mass of protonPlum Pudding Model16e- charge = -1.60 x 10-19 CThomsons charge/mass of e- = -1.76 x 108 C/ge- mass = 9.10 x 10-28 gMeasured mass of e- (1923 Nobel Prize in Physics)Millikans ExperimentErnest
10、Rutherford 1871-1937 Nucleus Theory 1910 alpha particle gold foil experiment An atoms mass is mostly in the nucleus The nucleus has a positive charge (Moseley) Electrons in fixed orbitRutherford Gold Foil Experiment Bombard the gold foil with alpha particles, positively charge particles w/ 4x of the
11、 mass of H Only expect slight deflection Evidence: Wide-angle deflectionClick for Interactive DemonstrationExperiment Conclusion atoms positive charge is concentrated in the nucleus Volume of a nucleus is very small compared with the total volume of an atom The nucleus is heavier than electron Sugge
12、sted that the atom might resemble a tiny solar system, with a massive, positively charged center circled by only a few electrons proton (p) has opposite(+)charge of electron (-) mass of p is 1840 x mass of e- (1.67 x 10-24 g)Rutherford ModelJames Chadwick 1891-1974 Worked with Rutherford Interpreted
13、 work of the Curies Discovered Neutron 1932 Nobel Prize in Physics 193522Chadwicks Experiment (1932) (1935 Noble Prize in Physics)H atoms - 1 p; He atoms - 2 pmass He/mass H should = 2measured mass He/mass H = 4a + 9Be1n + 12C + energyneutron (n) is neutral (charge = 0)n mass p mass = 1.67 x 10-24 g
14、The Neutron Chadwick 1932 - nuclear bombardment No charge n0 Actual Mass: 1.67 x 10-24g Relative Mass: 1Niels Bohr 1885-1962 Planetary Model 1913 Nucleus surrounded by orbiting electrons at different energy levels Electrons have definite orbits Utilized Plancks Quantum Energy theory Worked on the Ma
15、nhattan Project (US atomic bomb)Bohrs ModelBohr Model for NitrogenErnst Schrdinger 1887-1961 Quantum Mechanical Model 1926 Electrons are in probability zones called “orbitals”, not orbits and the location cannot be pinpointed Electrons are particles and waves at the same time Developed quantum numbers based on theories of Einstein and PlanckWerner Heisenberg 1901-1976OrbitalsQuantum Mechanical Theory Electron in a Hydrogen atomAtomic Theories TimelineNameDemocritusDaltonThomsonRutherfordBohrSchrdinger HeisenbergTime FrameKey PointsHistorical Events
