1 / 82

Chapter 2

Chapter 2. Atoms, Molecules, and Ions. History. Geeks…I mean Greeks Democritus and Leucippus - atomos Aristotle- elements. Alchemy 1660 - Robert Boyle- experimental definition of element. Lavoisier- Father of modern chemistry. He wrote the book. Laws. Conservation of Mass--Lavoisier

gustav
Download Presentation

Chapter 2

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter 2 • Atoms, Molecules, and Ions

  2. History • Geeks…I mean Greeks • Democritus and Leucippus - atomos • Aristotle- elements. • Alchemy • 1660 - Robert Boyle- experimental definition of element. • Lavoisier- Father of modern chemistry. • He wrote the book.

  3. Laws • Conservation of Mass--Lavoisier • Law of Definite Proportion- compounds have a constant composition.--Proust • The react in specific ratios by mass. • Multiple Proportions- When two elements form more than one compound, the ratios of the masses of the second element that combine with one gram of the first can be reduced to small whole numbers.--Dalton

  4. What?! • Water has 8 g of of oxygen per g of hydrogen. • Hydrogen peroxide has 16 g of oxygen per g of hydrogen. • 16/8 = 2/1 • Small whole number ratios. Mass of Nitrogen that combines with 1 g of oxygen Compound A 1.750g Compound B 0.8750g Compound C 0.4375g A/B= 1.750/0.8750 = 2/1 B/C=0.875/0.4375 = 2/1 A/C=1.750/0.4375=4/1

  5. Proof • Mercury has two oxides. One is 96.2 % mercury by mass, the other is 92.6 % mercury by mass. • Show that these compounds follow the law of multiple proportion. • Speculate on the formula of the two oxides.

  6. Dalton’s Atomic Theory • Elements are made up of atoms • Atoms of each element are identical. Atoms of different elements are different. • Compounds are formed when atoms combine. Each compound has a specific number and kinds of atom. • Chemical reactions are rearrangement of atoms. Atoms are not created or destroyed.

  7. A Helpful Observation • Gay-Lussac- under the same conditions of temperature and pressure, compounds always react in whole number ratios by volume. • Avagadro- interpreted that to mean • at the same temperature and pressure, equal volumes of gas contain the same number of particles. • (called Avagadro’s Hypothesis)

  8. Experiments to determine what an atom was • J. J. Thomson- used Cathode ray tubes

  9. Voltage source Thomson’s Experiment - +

  10. Voltage source Thomson’s Experiment - +

  11. Voltage source Thomson’s Experiment - + • Passing an electric current makes a beam appear to move from the negative to the positive end.

  12. Voltage source Thomson’s Experiment • By adding an electric field

  13. Voltage source Thomson’s Experiment + - • By adding an electric field, he found that the moving pieces were negative

  14. Thomsom’s Model • Found the electron. • Couldn’t find positive (for a while). • Said the atom was like plum pudding. • A bunch of positive stuff, with the electrons able to be removed.

  15. Atomizer Oil droplets + - Oil Telescope Millikan’s Experiment

  16. Millikan’s Experiment X-rays X-rays give some electrons a charge.

  17. Millikan’s Experiment Some drops would hover From the mass of the drop and the charge on the plates, he calculated the mass of an electron

  18. Radioactivity • Discovered by accident • Bequerel • Three types • alpha- helium nucleus (+2 charge, large mass) • beta- high speed electron • gamma- high energy light

  19. Rutherford’s Experiment • Used uranium to produce alpha particles. • Aimed alpha particles at gold foil by drilling hole in lead block. • Since the mass is evenly distributed in gold atoms alpha particles should go straight through. • Used gold foil because it could be made atoms thin.

  20. Florescent Screen Lead block Uranium Gold Foil

  21. What he expected

  22. Because

  23. Because, he thought the mass was evenly distributed in the atom.

  24. What he got

  25. + How he explained it • Atom is mostly empty • Small dense, positive pieceat center. • Alpha particlesare deflected by it if they get close enough.

  26. + Rutherford said that the results of the gold foil experiment were comparaable with shooting a howitzer at a piece of paper and having the shell reflect back.

  27. Modern View • The atom is mostly empty space. • Two regions • Nucleus- protons and neutrons. • Electron cloud- region where you might find an electron.

  28. Sub-atomic Particles • Z - atomic number = number of protons determines type of atom. • A - mass number = number of protons + neutrons. • Number of protons = number of electrons if neutral.

  29. Symbols A X Z 23 Na 11

  30. Chemical Bonds • The forces that hold atoms together. • Covalent bonding - sharing electrons. • Makes molecules. • Chemical formula- the number and type of atoms in a molecule. • C2H6 - 2 carbon atoms, 6 hydrogen atoms, • Structural formula shows the connections, but not necessarily the shape.

  31. H H • There are also other model that attempt to show three dimensional shape. • Ball and stick. H C C H H H

  32. Ions • Atoms or groups of atoms with a charge. • Cations- positive ions - get by losing electrons(s). • Anions- negative ions - get by gaining electron(s). • Ionic bonding- held together by the opposite charges. • Ionic solids are called salts.

  33. Polyatomic Ions • Groups of atoms that have a charge. • Yes, you have to memorize them. • List on page 65

  34. Periodic Table

  35. Metals • Conductors • Lose electrons • Malleable and ductile

  36. Nonmetals • Brittle • Gain electrons • Covalent bonds

  37. Semi-metals or Metalloids

  38. Alkali Metals

  39. Alkaline Earth Metals

  40. Halogens

  41. Transition metals

  42. Noble Gases

  43. Inner Transition Metals

  44. +1 +2 -3 -2 -1

  45. Naming compounds • Two types • Ionic - metal and non metal or polyatomics. • Covalent- we will just learn the rules for 2 non-metals.

  46. Ionic compounds • If the cation is monoatomic- Name the metal (cation) just write the name. • If the cation is polyatomic- name it. • If the anion is monoatomic- name it but change the ending to –ide. • If the anion is poly atomic- just name it • Practice.

  47. NAMING IONIC COMPOUNDS NaCl Rb2O CaS AlI3 CsF Li3N Al2O3 NaH CaBr2 Sr3P2

  48. NaCl Sodium Chloride Rb2O Rubidium oxide CaS Calcium Sulfide AlI3 Aluminum Iodide CsF Cesium Fluoride Li3N Lithium Nitride Al2O3 Aluminum Oxide NaH Sodium Hydride CaBr2 Calcium Bromide Sr3P2 Strontium Phosphide

  49. NAMING IONIC COMPOUNDS • KClO3 • Ca3PO4 • Al2(SO4)3 • K2Cr2O7 • BaSO3 • NaNO2 • KMnO4 • NH4NO3 • Al(OH)3 • Na2CrO4

  50. KClO3 Potassium Chlorate Ca3PO4 Calcium Phosphate Al2(SO4)3 Aluminum Sulfate K2Cr2O7 Potassium Chromate BaSO3 Barium sulfite NaNO2 Sodium Nitrite KMnO4 Potassium Permanganate NH4NO3 Ammonium Nitrate Al(OH)3 Aluminum Hydroxide Na2CrO4 Sodium Chromate

More Related