Unit # 4

1. Unit # 4 Atomic Theory

2. History Greeks • Democritus (460-370BC) – Matter is made of atoms. - Different kinds of shapes and sizes • Aristotle ( 364 -322 BC) • didn’t believe of atoms. • - Matter is made of earth, fire, air, and water.

3. 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.

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

5. Voltage source Thomson’s Experiment - +

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

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

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

9. 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.

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

11. 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.

12. Florescent Screen Lead block Uranium Gold Foil

13. What he expected

14. Because

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

16. What he got

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

18. + Inside the Gold atom

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

20. Chadwick 1932 • James Chadwick proves the existence of neutrons • He fired protons at Lithium nuclei, splitting them into helium nuclei and releasing energy.

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

22. Symbols A X Z 23 Na 11

23. How Atoms Differ • Atomic number = number of protons • Atomic number = number of electrons. • Number of Neutrons= mass # - Protons # • Problem:

24. Homework • How many electrons and protons are in each atom? Radon ; Magnesium • An atom contains 66 electrons. Which element is it? • An atom of an element contains 14 protons. Which element is it?

25. 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.

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

27. 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.

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

29. Periodic Table

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

31. Nonmetals • Brittle • Gain electrons • Covalent bonds

32. Semi-metals or Metalloids

33. Alkali Metals

34. Alkaline Earth Metals

35. Halogens

36. Transition metals

37. Noble Gases

38. Inner Transition Metals

39. +1 +2 -3 -2 -1

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

41. 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.

42. Covalent compounds • Two words, with prefixes. • Prefixes tell you how many. • mono, di, tri, tetra, penta, hexa, septa, nona, deca • First element whole name with the appropriate prefix, except mono. • Second element, -ide ending with appropriate prefix. • Practice

43. More Naming

44. 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

45. Ionic Compounds • Have to know what ions they form • off table, polyatomic, or figure it out • CaS • K2S • AlPO4 • K2SO4 • FeS • CoI3

46. Ionic Compounds • Fe2(C2O4) • MgO • MnO • KMnO4 • NH4NO3 • Hg2Cl2 • Cr2O3

47. Ionic Compounds • KClO4 • NaClO3 • YBrO2 • Cr(ClO)6

48. Naming Covalent Compounds • Two words, with prefixes • Prefixes tell you how many. • mono, di, tri, tetra, penta, hexa, septa, nona, deca • First element whole name with the appropriate prefix, except mono • Second element, -ide ending with appropriate prefix • Practice

49. Naming Covalent Compounds • CO2 • CO • CCl4 • N2O4 • XeF6 • N4O4 • P2O10

50. Writing Formulas • Two sets of rules, ionic and covalent • To decide which to use, decide what the first word is. • If is a metal or polyatomic use ionic. • If it is a non-metal use covalent.