1. Chapter 2 Atoms, Molecules & Ions

2. Atomic Theory Elements composed of atoms Atoms can’t be changed by “normal” chemical reactions Compounds of multiple atoms John Dalton

3. Conservation of Mass In ordinary chemical reactions, matter can be neither created nor destroyed

4. Constant Composition Compounds contain elements that are always in the same proportions

5. Period 2 stopped here 9/7/06

6. Multiple Proportions The elements making up a compound will form whole number ratios

7. Atom The smallest particle an element can be broken down into and still maintain the identity of the element

8. Nuclear Atom Proved by Rutherford & Bohr in the famous gold foil experimentsgold foil experiments

9. Subatomic CompositionComposition Proton: in the nucleus Neutron: in the nucleus Electron: outside the nucleus

10. Proton In Nucleus +1 relative charge About 1 amu in mass

11. Neutron In nucleus Neutral, zero charge Mass is about 1 amu

12. Electron Outside the nucleus -1 in relative charge Negligible mass about 1/2000 amu

13. Electron Charge Determined by Robert Milliken in the famous oil droplet experimentoil droplet experiment

14. Atomic Number The number of protons in an element Z number

15. Mass Number = number of protons and neutrons in an atom A - number

16. Nuclear Symbol A 4 X He Z 2 GeneralSpecific FormulaExample

17. Isotopes Atoms that contain the same number of protons, but different number of neutrons Z constant, A variable

18. Isotopes are useful! C 14 - dating Isotopic - tracing – Works like a flag – you can follow an atom or molecule through a reaction

19. Shorthand for isotopes Instead of full notation: 14 CWrite: C-14 6 So, only the A number (protons + neutrons)

20. Atomic Mass All elements have >1 isotope. The percentage of one isotope is its relative abundance. Atomic mass = (A # of isotope 1 x % isotope #1) + (A # of isotope 2 x % isotope # 2) + etc…

21. Periodic Table Hierarchy of all the elements. The order is used to predict size, charge, electronic structure & reactivity of elements

22. Periods Rows which indicate energy level or shell or size of the atoms

23. Groups or Families Columns which indicate the number of electrons in the outermost energy level determining charge & reactivity

24. Metals Left three quarters of the chart Lose electrons Become positive

25. Nonmetals Upper right portion Gain, lose, or share electrons when they react

26. Metalloids Along the stair-stepped line from B to At Share properties of metals & nonmetals

27. Radioactivity The spontaneous breakdown of an unstable nucleus

28. Compound A grouping of atoms that are chemically combined

29. Molecule A compound that can exist by itself

30. Diatomic Molecule Two atoms of the same element that are chemically combined Cl 2, F 2, O 2

31. Ion Charged Particle Cl -1

32. Polyatomic Ion A group of atoms chemically combined that together has a charge SO 4 -2

33. 9/7/06 period 1 stopped here

34. Binary Compound A compound made up of two elements in any ratio NaCl Mg 3 P 2

35. Chemical Formula A formula that shows the number and kinds of atoms in a compound CaCO 3

36. Molecular Formula A formula that shows the number and kinds of atoms in a molecule C 6 H 12 O 6

37. Period 4 stopped here 9/7/06

38. Atomic Structure List & describe the three subatomic particles

39. Atomic Structure Fill in the Chart: Isotope protons neutrons electrons U-235 - - - - 56 80 - - - 14 13

40. Calculate the atomic mass of the element made up of the following isotopes: 99.50 % H-1 0.30 % H-2 0.20 % H-3

41. Calculate Pt’s atomic mass : 5.0 % Pu-242 5.0 % Pu-243 80.0 % Pu-244 10.0 % Pu-245

42. Determine the number of atoms in each compound C 6 H 12 O 6 NaNO 3 H 3 PO 4 Al 2 (SO 4 ) 3