1 Chap 3: Atoms & the Periodic Table KMC Mrs. Chang.

1 Chap 3: Atoms & the Periodic Table KMC Mrs. Chang

2 Visual Concepts Law of Conservation of Mass Chapter 3

3 masses samples same Foundations of Atomic Theory The Laws of Definite and Multiple Proportions: The Laws of Definite and Multiple Proportions: Law of definite proportion- in samples of any chemical compound, the _____ of the ______ are always in the _____ proportions Law of definite proportion- in samples of any chemical compound, the _____ of the ______ are always in the _____ proportions ex: In water, there will always be 8 g O for 1 g of H. ex: In water, there will always be 8 g O for 1 g of H. 16 g O = 8 g O 2 g H1 g H 16 g 16 g 1 g1 g

4 Visual Concepts Law of Definite Proportions Chapter 3

5 Law of multiple proportion- whenever 2 elements form more than one compound, the ______ masses of one element that combine with the _____ mass of the other element are in the ratio of small whole numbers Law of multiple proportion- whenever 2 elements form more than one compound, the ______ masses of one element that combine with the _____ mass of the other element are in the ratio of small whole numbers Ex: compare water and peroxide. Ex: compare water and peroxide. Both molecules have the same number of H but different number of O, so the ratio is 1:2. Both molecules have the same number of H but different number of O, so the ratio is 1:2. water peroxide different same

6 Visual Concepts Law of Multiple Proportions Chapter 3

7 CO CO carbon monoxide carbon monoxide CO 2 CO 2 carbon dioxide carbon dioxide

8 Development of Atomic Models 1. Greek model(300’s BC): Democritus believed matter cannot be broken forever  _____ Democritus 2. Dalton’s atomic theory (pg 78): a. Elements are composed of indivisible atoms b. If same element, then same atoms c. Cannot be subdivided, created, or destroyed d. Can physically mix; can chemically combine in whole # ratio e. Chem. Rxn occur when atoms separate, join, or rearrange atoms

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Atomic Theory, continued Chapter 3 Section 1 Substances Are Made of Atoms The figure on the right is a more accurate representation of an atom than the figure on the left.

10 3. Goldstein (1886): discovered______, positive particles, observed canal rays traveling opposite cathode rays 4. Thomson: discovered __ using a cathode-ray tube(1897); its mass is about 1/2000 of a hydrogen atom(1900) Fig 3-4, 3-5 cathode-ray tubecathode-ray tube 5. Rutherford (1911): atom mostly empty space with dense _______ a. Fig 3-6: gold foil experiment gold foil experimentgold foil experiment b. Dodger stadium vs. marble 6. Millikan(1916): e- carries ___ ___ of negative charge and has a mass of ______ of a hydrogen atom 7. Chadwick (1932): discovered _______, no charge, same mass as a proton protons e- nucleus one unit 1/1840 neutron

11 Visual Concepts Thompson’s Cathode Ray Tube Experiment Chapter 3

12 Visual Concepts Rutherford’s Gold Foil Experiment Chapter 3

e - charge = -1.60 x 10 -19 C Thomson’s charge/mass of e - = -1.76 x 10 8 C/g e - mass = 9.10 x 10 -28 g Measured mass of e - (1923 Nobel Prize in Physics) 2.2

14 Visual Concepts Comparing Models of Atoms Chapter 3

16 3-2 Subatomic Particles Subatomic ParticlesSubatomic Particles 1. Nucleus: a. 99.9% mass b. Isotope: same # of ______, different # of _______; Isotope - ex. 3 different isotopes of Ne: Ne-20, Ne-21, Ne-22 c. p+ = 1 amu = 1/12 of a carbon-12 atom d. Mass # = ______ + _______ e. Atomic number = # of _______ 2. Electron: a. Around the nucleus in a specific energy level (Bohr) b. 1/1836 amu c. ______: can move from one energy level to another d. ______ _____: e- prefer to be at the lowest energy level protons neutrons protons excited Ground State

17 Tr 12A Table 3 p. 83 Properties of Subatomic Particles Which is the smallest? The Electron Describe the information conveyed by each symbol. The 1st symbol only shows the relative charge (use when that’s all you need). The 2nd also shows the mass number.

18 Most of the atom’s mass. NUCLEUSELECTRONS PROTONSNEUTRONS NEGATIVE CHARGE POSITIVE CHARGE NEUTRAL CHARGE ATOM QUARKS Atomic Number equals the # of... equal in a neutral atom Subatomic Particles Subatomic Particles

19 B. Isotopes Atoms of the same element with different mass numbers. Atoms of the same element with different mass numbers.element Mass # Atomic # Nuclear symbol: Nuclear symbol: Hyphen notation: carbon-12 Hyphen notation: carbon-12

21 B. Isotopes © Addison-Wesley Publishing Company, Inc.

22 B. Isotopes Isotopes Chlorine-37 Chlorine-37 atomic #: atomic #: mass #: mass #: # of protons: # of protons: # of electrons: # of electrons: # of neutrons: # of neutrons:1737171720

Symbols Contain the symbol of the element, the mass number and the atomic number. Contain the symbol of the element, the mass number and the atomic number. We can also put the mass number after the name of the element for different isotopes We can also put the mass number after the name of the element for different isotopes carbon- 12, carbon -14 carbon- 12, carbon -14 X Mass number Atomic number

Example Problem 1. Give the Atomic number of the element shown. F 19 9 Ans. 9 2 Give the number of protons and electrons for this element. 2. Give the number of protons and electrons for this element. Ans. 9 p + and 9 e - 3. Give the mass number of the element shown. Ans. 19 4Give the number of neutrons for this element. 4. Give the number of neutrons for this element. Ans. 10 # of n 0 = mass # - atomic # # of n 0 = 19 – 9 = 10 n 0

25 HW HW 1. Write a song using structure of an atom: include 7 key terms used in context (from section 2) 2. Draw any diagram depicting the song/ poem, color 3-4 colors

3-4: Atomic Mass Periodic Table shows the average atomic mass. Periodic Table shows the average atomic mass. Based on abundance of each element in nature. Based on abundance of each element in nature. Don’t use grams because the numbers would be too small. Don’t use grams because the numbers would be too small. Each isotope has its own atomic mass, thus we determine the average from percent abundance. Each isotope has its own atomic mass, thus we determine the average from percent abundance. Is not a whole number because it is an average. Is not a whole number because it is an average.

27 Chemical Quantities? Chemical Quantities? You can measure mass, volume,or you can count particles. You can measure mass, volume,or you can count particles. measure mass in grams. measure mass in grams. measure volume in liters. measure volume in liters. We count particles in MOLES. We count particles in MOLES. Mole is abbreviated: mol Mole is abbreviated: mol

28 What is the Mole? A counting number (like a dozen) 6.02 x 10 23 is called Avogadro’s number. 1 mol = 6.02  10 23 items ( representative particles) A large amount!!!!

29 1 mole of hockey pucks would equal the mass of the moon! 1 mole of hockey pucks would equal the mass of the moon! 1 mole of pennies would cover the Earth 1/4 mile deep! 1 mole of pennies would cover the Earth 1/4 mile deep! 1 mole of basketballs would fill a bag the size of the earth! 1 mole of basketballs would fill a bag the size of the earth!

30 Molar Conversion Examples How many atoms are in 2.50 moles of C? How many atoms are in 2.50 moles of C? 2.50 mol 6.02  10 23 atoms 1 mol 1.51  10 24 1.51  10 24 =atoms C =atoms C

31 1. Calculate the # of atoms in 0.500 mol of Al. 1) Ans: 3.01 x 10 23 Al atoms 0.500 mol Al x 6.02 x 10 23 Al atoms 1 mol Al Example 2. Calculate the # of moles of Na if a sample of Na contains 1.80 x 10 24 Na atoms. 2) Ans: 2.99 mole Na 1.8 x 10 24 Na atoms x 1 mol Na 6.02 x 10 23 Na atoms 6.02 x 10 23 Na atoms

32 Molar Mass - Is the Mass (in Grams) of One Mole of a Substance (often called molecular weight) Molar mass or ___ is the generic term for the mass of one mole of any substance (in grams) Molar mass or ___ is the generic term for the mass of one mole of any substance (in grams) The same as: The same as: 1) gram molecular mass or ___ (molecules) 2) gram formula mass or ___ (ionic compounds) 3) gram atomic mass or ___ (elements) MM gmm gfm gam

33 Molar Mass of Elements = atomic mass (simply look at the periodic table) carbon carbon aluminum aluminum zinc zinc 12.01 g/mol 26.98 g/mol 65.39 g/mol

34 Mass to Mole Conversion How many moles of carbon is 26 g of carbon? (find MM of C from the periodic table) How many moles of carbon is 26 g of carbon? (find MM of C from the periodic table) 26 g C 1 mol C 12.01 g C = 2.2 mol C

35 1 mol Na 22.99 g Na Mass to Mole Conversion How many moles is 5.69 g of Na? How many moles is 5.69 g of Na? Na = 22.99 g/mol Na = 22.99 g/mol 5.69 g Na = 0.247 mol Na

36 Mole to Mass Conversion How many grams are in 9.45 mol of nitrogen atoms? How many grams are in 9.45 mol of nitrogen atoms? N = 14.01 g/mol N = 14.01 g/mol 9.45 mol N 14.01 g N 1 mol N = 132.39 =132 g N

37 Test Prep: How many moles of carbon-12 are contained in exactly 6 grams of carbon- 12? 1. 0.5mole 2. 2.0moles 3. 3.01 ×10 23 moles 4. 6.02 ×10 23 moles

Test Prep 38 How many atoms are contained in 97.6 g of platinum (Pt)? 1. 5.16 × 10 30 2. 3.01 × 10 23 3. 1.20 × 10 24 4. 1.10 × 10 28

39 Molar Conversions molar mass (g/mol) MASS IN GRAMS MOLES NUMBER OF PARTICLES 6.02  10 23 (particles/mol) ÷ X÷ X

41 What about compounds? Mass in grams of 1 mole equal the sum of the atomic masses Mass in grams of 1 mole equal the sum of the atomic masses What is the mass of one mole (molar mass) of CH 4 ? What is the mass of one mole (molar mass) of CH 4 ? 1 C x 12.01 g/mol = 12.01 g/mol 4 H x 1.01 g/mol = 4.04g/mol 1 mole CH 4 = 12.01g/mol + 4.04 g/mol =16.05g/mol

42 Molar Mass Example Problem Find the molar mass of sodium bicarbonate NaHCO 3 NaHCO 3 22.99g/mol + 1.01g/mol + 12.01g/mol + 3(16.00 g/mol) = 84.01 g/mol 22.99g/mol + 1.01g/mol + 12.01g/mol + 3(16.00 g/mol) = 84.01 g/mol

43 Prozac, C 17 H 18 F 3 NO, is a widely used antidepressant that inhibits the uptake of serotonin by the brain. It has a molar mass of 1) 40.0 g/mole 2) 262 g/mole 3) 309 g/mole Example Problem Solution: 17C (12.0) 18H (1.0) 3F (19.0) 1N (14.0) + 1 O (16.0) 309 g/mole

44 1 mol NaOH 40.00 g NaOH Mass to Mole Conversion How many moles is 5.69 g of NaOH? (Find MM of NaOH) How many moles is 5.69 g of NaOH? (Find MM of NaOH) Na = 22.99 g/mol Na = 22.99 g/mol O = 16.00 g/mol O = 16.00 g/mol H = 1.01 g/ mol H = 1.01 g/ mol 40.00 g/mol 40.00 g/mol 5.69 g NaOH = 0.142 mol NaOH

45 Mole to Mass Conversion How many grams are in 9.45 mol of dinitrogen trioxide? How many grams are in 9.45 mol of dinitrogen trioxide? N 2 O 3 = 2(14.01) + 3(16.00) = 76.02 g/mol N 2 O 3 = 2(14.01) + 3(16.00) = 76.02 g/mol 9.45 mol N 2 O 3 76.02 g N 2 O 3 1 mol N 2 O 3 = 718.2 =718 g N 2 O 3

46 Representative particles The smallest pieces of a substance. The smallest pieces of a substance. molecular compounds: molecule. molecular compounds: molecule. ionic compounds: formula unit. ionic compounds: formula unit. elements: atom. elements: atom.

47 Questions How many atoms in the following cmpds? How many atoms in the following cmpds? CaCO 3 CaCO 3 5 Al 2 (SO 4 ) 3 Al 2 (SO 4 ) 3 17 17 How many oxygen atoms in the above cmpds? How many oxygen atoms in the above cmpds? 3 12 12

48 Contains 6.02 x 10 23 particles 1 mole C = 6.02 x 10 23 C atoms 1 mole H 2 O = 6.02 x 10 23 H 2 O molecules 1 mole NaCl = 6.02 x 10 23 NaCl formula units A Moles of Particles

52 Another Example How many molecules of CO 2 are there in 1.23 moles of CO 2 ? …how many oxygen atoms? How many molecules of CO 2 are there in 1.23 moles of CO 2 ? …how many oxygen atoms? 1.23 mol CO 2 1 mol CO 2 6.02 x 10 23 molecules CO 2 1 molecule CO 2 2 atoms O = 7.40 x 10 23 molecules of CO 2 = 1.48 x 10 24 atoms O

53 More Molar Conversion Examples Find the mass of 2.1  10 24 molecules of NaHCO 3. Find the mass of 2.1  10 24 molecules of NaHCO 3. 2.1  10 24 molecules 1 mol 1 mol 6.02  10 23 molecules = 290 g NaHCO 3 84.01 g 84.01 g 1 mol 1 mol

54 Practice Problems 1. How many moles is 4.56 g of CO 2 ? 2. How many grams is 9.87 moles of H 2 O? 3. How many molecules is 6.8 g of CH 4 ? 4. How much would 3.45 x 10 22 atoms of U weigh? =.104 mol = 178 g = 2.6 x 10 23 molec = 13.6 g

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 2. Which of these is always equal to the number of protons in an atom? F.the mass number G.the number of isotopes H.the number of neutrons I.the number of electrons Understanding Concepts Chapter 3 Standardized Test Preparation

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 2.Which of these is always equal to the number of protons in an atom? F.the mass number G.the number of isotopes H.the number of neutrons I.the number of electrons Understanding Concepts Chapter 3 Standardized Test Preparation

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 3. Which of these events occurs when an electron in an excited state returns to its ground state? A.Light energy is emitted. B.Energy is absorbed by the atom. C.The atom undergoes spontaneous decay. D.The electron configuration of the atom changes. Understanding Concepts Chapter 3 Standardized Test Preparation

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 7. The model of the atom has changed over time because F.earlier models were proven to be wrong. G.electrons do not revolve around the nucleus. H.as new properties of atoms were discovered, models had to be revised to account for those properties. I.new particles were discovered, so the model had to be changed to explain how they could exist. Reading Skills Chapter 3 Standardized Test Preparation

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 8. Why do scientists need models as opposed to directly observing electrons? A.Models can be changed. B.There is no technology that allows direct observation of electrons. C.The charges on the electrons and protons interfere with direct observation of the atom. D.Scientists cannot measure the speed of electrons with sufficient accuracy to determine which model is correct. Reading Skills Chapter 3 Standardized Test Preparation

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 9. What would cause scientists to change the current model of the atom? Reading Skills Chapter 3 Standardized Test Preparation

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 9. What would cause scientists to change the current model of the atom? Answer: The current model of the atom would change if new data were found about atoms that could not be explained by the existing model. The new model would explain both the new data and all earlier observations. Reading Skills Chapter 3 Standardized Test Preparation

Thomson’s Experiment Voltage source +- Vacuum tube Metal Disks

66 Some History on The Discovery of the Atom Discovery of The Electron: J.J. Thomson and the Cathode Ray Tube (1897) Calculated e-/m

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

Thomson’s Experiment n By adding an electric field + -

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

Rutherford’s experiment Alpha particles - positively charged particles- helium atoms minus electrons Alpha particles - positively charged particles- helium atoms minus electrons Shot them at gold foil which can be made a few atoms thick. Shot them at gold foil which can be made a few atoms thick. When an alpha particle hits a fluorescent screen, it glows When an alpha particle hits a fluorescent screen, it glows

71 Some History on The Discovery of the Atom Rutherford’s Gold Foil Experiment and Rutherford’s Gold Foil Experiment and the Discovery of the Nucleus Believed in Plum Pudding Model Wanted to see How Large Atoms are

Lead block Uranium Gold Foil Fluorescent Screen

He Expected The alpha particles to pass through without changing direction very much. The alpha particles to pass through without changing direction very much. Because…? Because…? …the positive charges were thought to be spread out evenly. Alone they were not enough to stop the alpha particles. …the positive charges were thought to be spread out evenly. Alone they were not enough to stop the alpha particles.

What he expected

Because

He thought the mass was evenly distributed in the atom

Since he thought the mass was evenly distributed in the atom

What he got

How he explained it + Atom is mostly empty. Atom is mostly empty. Small dense, positive piece at the center-- Small dense, positive piece at the center-- the nucleus. the nucleus. Alpha particles are deflected by it, if they get close enough. Alpha particles are deflected by it, if they get close enough.

+ Almost no deflection; few greatly deflected Almost no deflection; few greatly deflected

History of Atom Democritus looked at beach (400 B.C.) Democritus looked at beach (400 B.C.) Made of sand Made of sand Cut sand - smaller sand Cut sand - smaller sand n Smallest possible piece? n Atomos - not to be cut

1 Chap 3: Atoms & the Periodic Table KMC Mrs. Chang.

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