WU: A number is not a measurement without a Thermal expansion of metals = draw a particle drawing of a solid under these 3 conditions 30 o C, room temp, 1000 o C What is air made of? What does the law of conservation of mass say about the mass before a reaction and after a reaction? Reactants yield products Compare and contrast a Theory and a Law Warm Up 1: CH 4 RG Pass it up! What is the difference between an element, cmpd, atom, and subatomic parcle? Element Cmpd Atom Subatom Part Feb 5 8:35 AM Jan 31 3:32 PM The Beginning of the Atom Democritus s Atomic Philosophy 460BC 370BC ~ Believed atoms were indivisible and indestrucble Dalton took it and ran with it 2000 yrs later! Dalton: circa 1800: Back in the day this is all they "knew" (or at least theorized). Atoms are indivisible (today known to be FALSE b/c know about subatomic particles!) In any sample of a pure element, all the atoms are identical in mass and other properties. (today known to be FALSE b/c know about isotopes!) Atoms of one element are different from atoms of another element (still true) Atoms combine in simple whole number ratios (called Law of Multiple Proportions) During reactions atoms are rearranged but unchanged (relates to Law of Cons of Matter) Jan 31 3:33 PM Jan 31 4:08 PM 1
Cathode Ray Tube (CRT) At low pressures, current flows through a gas. Experimentation shows: Glow on the glass opposite the cathode Different gases cause different color glows Paddle wheel in the middle spins bc bombarded with e- Conclusions: Cathode rays are composed of particles. Rays are deflected away from the negative pole of a magnet!) Therefore: particles are negative!!!!!!!!!!!!!!!!!! Cathode rays are deflected by external electric and magnetic fields. http://www.youtube.com/watch? v=7yhwmwcxex8&safety_mode=true&persist_safety_mode=1 Jan 31 4:09 PM Jan 31 4:09 PM JJ Thomson (1897) ~ Concluded that cathode rays were beams of identical, negatively charged particles (he did all of the stuff explained before...) ~ Called them electrons ~ Studied deflection of cathode rays and found that: Heavier (subatomic) particles were deflected less with magnet > More charge = more deflection (why b/c higher repulsion!) > e- has mass and a charge; and that its mass-to-charge ratio was much smaller than that of the hydrogen ion > 2 particles with the same mass-to-charge ratio move in the same path in a vacuum when subjected to the same electric and magnetic fields. Robert Milikan (1909)Preformed the oil drop experiment Drops fall due to gravity X ray put a negave charge on drops He measure charge on the drops Measured the amount of charge for each e then using Thomson s rao calculated the mass of an electron JJ's Model = Plum Pudding Model YUM!!!! This is what he did with a short explanation http://www.youtube.com/watch?v=xmfyhag7liw Jan 31 4:12 PM Jan 31 4:20 PM 2
Honors Chem Unit 2 Notes PToE and Atomic Struct 1.31.13.notebook Ernest Rutherford (1912) performed the gold foil experiment (Figure 4.7 pg 107) shot positively charged alpha particles at a piece of gold foil Eugene Goldstein Modified a cathode ray tube Found positive charge in the atom (actually was first to discover the positive charge but never coined the term "proton") Predicted that parcles would pass through b/c atom is mostly empty space 99% did 1 % were deflected ~2000X heavier than the e- Jan 31 4:21 PM concluded that there was a concentrated posive center (w/all mass!) in the atom... later coined the term "proton" Jan 31 4:21 PM James Chadwick (1932) Rutherford s model (and final conclusions): discovered the neutron The posive center was called the nucleus suspected purpose is to hold the protons in the nucleus together (it is the peacekeeper of the protons!) Most of the atom is empty space e are outside of the nucleus Watch this! Summary of JJ Thompson & Rutherford Animations Jan 31 4:22 PM Jan 31 4:22 PM 3
Niels Bohr: ~ Revised Rutherford s model to show electrons traveling around the nucleus in ENERGY LEVELS CALLED ORBITS!!!! ~ e s orbit the nucleus in SET PATHS ~ His model is called the planetary model. There are only 4 (visible) energy levels available to H The e s are quanzed (have a specific amount of energy) The spectra lines are formed when an e is moving between 2 energy levels or orbits (see below, light energy released!) We will talk a LOT more about this so don't be too worried if it looks difficult... Spectra! Watch this! http://www.learnerstv.com/animation/animation.php?ani=124&cat=chemistry Feb 7 4:19 PM Feb 7 4:24 PM Schrödinger : > e are quanzed (like what Bohr said) > Does not define a specific path or orbit of an e instead e s are free to move around the nucleus (opposite of Bohr) > Esmates the probability of finding an electron in a parcular region of space around the nucleus called an electron cloud. The Elements http://www.youtube.com/watch?v=zgm wskfbpo http://www.youtube.com/watch?v=uwmtorux0 Feb 2 3:23 PM Jan 31 4:23 PM 4
The Atomic Timeline Work with a partner of your choice!! Plan it out and leave space on your project for the Modern Models (learn next week!) Please be sure to include all of the info asked for! Historical Model of the Atom Project: You may complete this individually or as a partnership e following people were important scientists who worked on the question What is matter made of? Some of them made discoveries of batomic particles, while others developed a model for the atom. Mendeleev, Millikan, JJ Thomson, Chadwick, Rutherford, Dalton, Bohr, Schrodinger u are to make a History Booklet and 3D model which gives background information and facts about their scientific contributions to the olution of the atomic model. rt I: r each scientist, answer the following questions (they may be listed in bullet points) Who (under who you may include an interesting fact about his career or life) What was their discovery or model (describe it fully) o What experiment was used? (may not apply to all) o What were the results of the experiment? (may not apply to all) o What conclusions were drawn from the results? (may not apply to all) o What information the scientist used from his predecessors? When the discovery was reported and what was the reaction of the scientific community? Which parts of the model or discovery are known to be true today? For the areas in which the scientist was wrong, why were the wrong statements important? Must include a picture of the model or scientists Part II: Create a 3D representation of one of the atomic models to accompany your History Booklet. 3D model must be at least 6 inches in diameter Identify the title of the model and the scientists that is was attributed by Label necessary areas of the model (e-, p+, nucleus, orbitals, etc) EXTRA CREDIT: Include major worldwide events occurring at the time the discoveries were reported!! http://atomictimeline.net/index.php Jan 31 4:24 PM 5