1. LECTURE 3 ATOMS & MOLES

2. It all starts with….. The Law of Conservation of Mass Mass is neither created nor destroyed in a chemical reaction Huh? You can’t make stuff up or make it go away just because you want to “Stuff” just gets moved around

3. Law of Conservation of Mass Section 1 Substances Are Made of Atoms Chapter 3

4. Visual Concepts Law of Conservation of Mass Chapter 3

5. Law of Conservation of Mass, continued Section 1 Substances Are Made of Atoms Chapter 3

6. Dalton’s Theory All matter is made up of tiny particles called atoms Atoms of the same element are identical in size, mass, properties Atoms cannot be subdivided, created or destroyed Atoms of different elements combine to form chemical compounds

7. How much of this is true? Some of Dalton’s Theory about the atom has been altered based on new information This gives us the …..

8. Modern Atomic Theory All matter is made up of atoms. Atoms of the same element are chemically similar Atoms of an element may not have the same mass (Isotopes) Atoms are not subdivided, created or destroyed in chemical reactions.

9. Visual Concepts Isotopes and Nuclides Chapter 3

10. Isotopes Atoms of the same element with different masses Protons are the same Neutrons differ Looks like: uranium-235 Or

11. What else do we know?

12. Discovering the Electron Cathode Ray Tube Produces a charged ray When a positive magnet is placed near the ray, the ray bends towards the + magnet Thomson determined the electron was negative

13. Visual Concepts Thompson ’ s Cathode Ray Tube Experiment Chapter 3

14. Discovering the Electron Millikan’s Oil Drop Experiment What does it look like? It weighs 9.109 x 10 -31 kg

15. What about the Nucleus? Fired alpha particles (Helium) through thin sheets of gold Most particles went completely through Few were deflected

16. Visual Concepts Rutherford ’ s Gold Foil Experiment Chapter 3

17. Their conclusion … The nucleus: Small Dense (meaning heavy and packed) Positively charged Contains the protons and neutrons In summary…

18. Visual Concepts Comparing Models of Atoms Chapter 3

19. Which picture is more accurate?

20. Visual Concepts Parts of an Atom Chapter 3

21. Atomic Number It represents the # of protons It can also represent the # of electrons if the atom is neutral

22. Mass Number Represents the # of protons + # of neutrons Neutrons by itself = Mass Number – Atomic Number

23. Reviewing the Numbers Atomic Number

24. Reviewing the Numbers Mass Number

25. Sample Problem A How many protons, electrons, and neutrons are there in an atom of chlorine-37?

26. Sample Problem A How many protons, electrons, and neutrons are there in an atom of chlorine-37? ProtonsElectronsNeutrons Atomic # Mass # - Atomic # ???

27. Sample Problem A How many protons, electrons, and neutrons are there in an atom of chlorine-37? ProtonsElectronsNeutrons Atomic # Mass # - Atomic # 17 20

28. Now it’s your turn … Atomic Math Worksheet

29. The Mole & Avogadro’s Number

30. The Mole The amount of any substance that contains the same number of particles found in 12 g of Carbon-12 It’s a unit Abbreviate “mol”

31. Avogadro’s Number The Number of particles in one mole of any substance 6.022 x 10 23 atoms / ions / particles / compounds / etc.

32. Yup! More units….. That means we…… CONVERT!!!!

33. The Mole Map

34. Solving Mol – g Problems

35. Sample Problem B How many grams of He are there in 2.00 moles?

36. Sample Problem B Step 1: Start with what you know from the problem. 2.00 mol He How many grams of He are there in 2.00 moles?

37. Sample Problem B Step 2: What is the mass of He? (Look at the P.T.) 4.00 g / mol He How many grams of He are there in 2.00 moles?

38. Sample Problem B Step 3: Set-up the problem so the units cancel out. How many grams of He are there in 2.00 moles?

39. Sample Problem C What is the mass in grams of 3.50 mol of copper, Cu?

40. Sample Problem C What is the mass in grams of 3.50 mol of copper, Cu? Step 1: Start with what you know from the problem. 3.50 mol Cu

41. Sample Problem C What is the mass in grams of 3.50 mol of copper, Cu? Step 2: What is the mass of Cu? (Look at P.T.) 63.55 g / mol

42. Sample Problem C What is the mass in grams of 3.50 mol of copper, Cu? Step 3: Set-up the problem so the units cancel out.

43. Sample Problem D A chemist produced 11.9 g of aluminum, Al. How many moles of aluminum were produced?

44. Sample Problem D A chemist produced 11.9 g of aluminum, Al. How many moles of aluminum were produced? Step 1: Start with what you know from the problem. 11.9 g Al

45. Sample Problem D A chemist produced 11.9 g of aluminum, Al. How many moles of aluminum were produced? Step 2: What is the mass of Al? 26.98 g / mol Al

46. Sample Problem D A chemist produced 11.9 g of aluminum, Al. How many moles of aluminum were produced? Step 3: Set-up the problem so units cancel out.

47. Now it’s your turn …. Mole Conversions # 1