1. Chemistry: Chapter 3 Elements, Atoms, Ions

2. 3-1: The Elements Nature uses a relatively small number of fundamental units to assemble extremely complex materials 88 elements occur naturally; others made in lab

3. 3-2: Atoms & Compounds Democritus (~450 BC) All matter is composed of tiny, indivisible particles Atomos

4. 3-2: Atoms & Compounds Proust (1799) Law of Constant Composition--a compound will always contain the same elements in the same proportions by mass.

5. 3-2: Atoms & Compounds Dalton (1803) Atomic Theory of Matter Elements are made of atoms Atoms of an element are identical Atoms of an element are unique from any other element A compound always has the same proportion & kind of atoms Atoms are neither created nor destroyed in any chemical reaction

6. 3-2: Atoms & Compounds Compounds: Represented by chemical formulas Indicate the numbers of each element found in the compound NaCl

7. 3-3: Atomic Structure J.J. Thomson (1896) Studies with cathode ray tubes showed atoms of any element could be made to emit tiny negative particles = ELECTRONS!

8. 3-3: Atomic Structure J.J. Thomson (1896) Proposed the Plum Pudding Model (with Lord Kelvin) Electrons embedded in a positively charged spherical cloud Think “chocolate chip cookie dough” model

9. 3-3: Atomic Structure Ernest Rutherford (1911) Studied alpha (  ) particles Conducted Gold Foil Experiment

10. 3-3: Atomic Structure Ernest Rutherford: Gold Foil Experiment Directed alpha particles at thin gold foil, surrounded by detector that flashed when hit Most particles passed through, some deflected at large angles, some reflected backward

11. 3-3: Atomic Structure Ernest Rutherford (1911) Said atoms must have a small, dense, positive core (nucleus) around which tiny electrons move Concluded that protons make up the nucleus, with an equal but opposite charge of electrons In 1932 (with Chadwick)—showed that nuclei contain neutral particles called neutrons (slightly more massive than p+)

12. 3-3: Atomic Structure Modern Atomic Theory Central nucleus: Protons (1+) Neutrons (0) Electron Cloud Electrons (1-) far from nucleus

13. 3-3: Atomic Structure How big are they? Masses: Neutron > proton >>> electron

14. 3-3: Atomic Structure Isotopes—atoms with the same # of protons but different # of neutrons

15. 3-3: Atomic Structure Atomic number = to # protons Mass number = to #protons + #neutrons Essentially all mass comes from nucleus

16. Complete element symbol:

17. 3-4: Periodic Table Dmitri Mendeleev (1869) arranged first periodic table

18. 3-4: Periodic Table Element Song!!! http://www.privatehand.com/flash/elements.h tml http://www.privatehand.com/flash/elements.h tml

19. 3-4: Mendeleev’s Table Elements in column had similar properties Elements arranged by atomic mass Undiscovered elements were predicted

20. 3-4: Periodic Table Moseley (1913)—assigned atomic numbers to each element Arranged periodic table by atomic number

21. 3-4: Periodic Table Groups or Families—elements with similar properties; vertical columns Group 1A—alkali metals (highly reactive; never uncombined) Video of Alkali Metal Reactivity Video of Alkali Metal Reactivity Alkali Metal Reactivity Video (Brainiac) Alkali Metal Reactivity Video (Brainiac) Group 2A—alkaline earth metals (similar to group 1A)

23. 3-4: Periodic Table Groups or Families cont… Transition Metals Group 7A—halogens (highly reactive; never uncombined) Group 8A—noble gases (nonreactive)

25. 3-4: Periodic Table Periods--horizontal rows Periods--horizontal rows

26. 3-4: Periodic Table Metals (to the left of the semimetal line) Luster/shine, good conductors, malleable and ductile, usually solids at room temperature

28. 3-4: Periodic Table Nonmetals (to the right of the semimetal line) Not shiny, poor conductors, not malleable or ductile

30. 3-4: Periodic Table Semimetals (or metalloids)—found along the semimetal line There are seven: boron, silicon, germanium, arsenic, antimony, tellurium, astatine They have intermediate properties or some of both

32. 3-4: Periodic Table Diatomic Molecules— composed of two atoms (do not exist as single atoms) H 2, N 2, O 2, F 2, Cl 2, Br 2, I 2 (“Hy-7”)

34. 3-5: Ions & Their Compounds Atoms are neutral; they have an equal number of electrons and protons Ions—charged particle due to the loss or gain of electrons

35. 3-5: Ions & Their Compounds Two types of ions: Cation— “+” ion formed by losing electron(s) Anion—“-” ion formed by gaining electron(s) Named with an “-ide” ending

36. 3-5: Ions & Their Compounds Periodic trends in charges of ions; Group 1A—lose 1 electron = 1+ Group 2A—lose 2 electrons= 2+ Group 3A—lost 3 electrons = 3+ (mostly) Group 5A—gain 3 electrons = 3- (mostly) Group 6A—gain 2 electrons = 2- Group 7A—gain 1 electron = 1-

38. 3-5: Ions & Their Compounds Ionic compounds—formed by metal & nonmetal exchanging electrons to become ions Net charge = zero

39. 3-5: Ions & Their Compounds Properties of Ionic Compounds: Hard, brittle, crystalline solids at room temp. High melting point and boiling pt + & - charges attract very strongly

40. 3-5: Ions & Their Compounds

41. Properties of Ionic Compounds: Conducts electricity when melted or dissolved Substances that contain ions can only conduct when ions can move Electric current = moving electrons

42. 3-5: Ions & Their Compounds

43. 11-4: Periodic Trends Chemical Activity Most active metals : lower left (Fr) Most active nonmetals : upper right (F)

44. 11-4: Periodic Trends Atomic Size Increases down groups Additional levels = bigger atom Decreases across periods Increased “+” charge of nucleus pulls e-’s closer

45. 11-4: Periodic Trends Ionization Energy—energy required to remove an e- from an atom Metals = lower ionization energy E- not held as strongly Nonmetals = higher ionization energy IE increases across period 1A really wants to get rid of e-; 7A does NOT! Fr = lowest I.E. F = highest I.E. (besides noble gases)

46. 11-4: Periodic Trends

47. Electron Affinity The change in energy when an electron is added to an atom to make a negative ion OR: how likely an atom is to gain an e- Metals = lower e- affinity Want to lose e-; nuclei do not have a strong pull on their e- (val e- farther from nucleus) Nonmetals = higher e- affinity Want to gain e-; val e- closer to nucleus so easier to attract more e-

48. 11-4: Periodic Trends

49. Correlates to size… The closer the electrons are to the nucleus, the higher the affinity. Exception: fluorine (it’s already too full…)

50. P403-404: Electronegativity Electronegativity—tendency of an atom in a molecule to attract electrons to itself  Trend in electronegativity: Increases across, decreases down o Fluorine is highest = 4.0; Cesium & Francium are lowest = 0.7  The polarity of a bond depends on the difference in e.neg.; e- closer to more e.neg atom