1. 2-1 CHEM 100, FALL 2011 LA TECH Instructor: Dr. Upali Siriwardane e-mail: upali@chem.latech.edu Office: CTH 311 Phone 257-4941 Office Hours: M,W, 8:00-9:00 & 11:00-12:00 a.m Tu,Th,F 9:00 - 10:00 a.m. Test Dates : March 25, April 26, and May 18; Comprehensive Fina Exam: 9:30-10:45 am, CTH 328. Chemistry 100(02) Fall 2011 October 3, 2011 (Test 1): Chapter 1 & 2 October 26, 2011 (Test 3): Chapter 3 & 4 November 16, 2011 (Chapter 5 & 6) November 17, 2011 (Make-up test) comprehensive: Chapters 1-6 9:30-10:45:15 AM, CTH 328

2. 2-2 CHEM 100, FALL 2011 LA TECH Chapter 2. Elements & Atoms 2.1 Atomic Structure and Subatomic Particles 2.2 The Nuclear Atom 2.3 The Size of Atoms and Units Used to represent them 2.4 Uncertainty and Significant Figures 2.5 Atomic Numbers and Mass Numbers 2.6 Isotopes and Atomic Weights 2.7 Amount of Substances-The mole 2.8 Molar Mass and Problem Solving 2.9 The Periodic Table

3. 2-3 CHEM 100, FALL 2011 LA TECH Chapter 2. KEY CONCEPTS Elements & Atoms Radioactivity Subatomic Particles Electrons Electronic Charge Nuclear atom Protons Neutrons Atomic number (Z) Size of Atoms SI Units Unit Conversions Mass Numbers Isotopes Isotopic symbols Atomic Mass Units Mass Spectrometer isotope masses and % composition? Average atomic weights Periodic Table Abundance of Elements Earth's Atmosphere

4. 2-4 CHEM 100, FALL 2011 LA TECH Atomic Structure Early experiments showed the atom was composed of three subatomic particles: Electron, proton and neutron. The key discoveries: Radioactivity Becquerel (1896) – Uranium ore emits rays that “fog” a photographic plate. Marie and Pierre Curie (1898) – Isolated 2 new elements (Po and Ra) that did the same. radioactivity – Marie Curie called the phenomenon radioactivity.

5. 2-5 CHEM 100, FALL 2011 LA TECH Radioactivity Types of Radiation Alpha rayα (positive charge) Beta rayβ (negative charge) Gamma rayγ (no charge) Electrical behavior:+ attracted to - (opposites attract) (like charges repel) (like charges repel) Radioactive material Electrically Charged plates screen + − Beam of α, β, and γ α γ β

6. 2-6 CHEM 100, FALL 2011 LA TECH Electrons Thomson (1897) studied cathode rays and discovered the electron: Beam travels from the cathode (-) to the anode (+). – the beam flies through a ring anode and hits a fluorescent screen. The cathode rays come from the cathode metal. They are negative particles – electrons (e − ). fluorescent screen – high voltage + cathode ray

7. 2-7 CHEM 100, FALL 2011 LA TECH Electrons Thomson showed that electric and magnetic fields deflect the beam. – – high voltage + + From the deflections, Thomson calculated the mass/charge ratio for an e - : = −5.60 x 10 -9 g/C (Coulomb (C) = the SI unit of charge)

8. 2-8 CHEM 100, FALL 2011 LA TECH Electronic Charge Robert Millikan (1911) studied electrically- charged oil drops. For a single charged drop, he measured: – the time to fall a fixed distance, and – to rise the same distance in an electric field. He showed that each drop had a charge that was an integer multiple of −1.60 x 10 -19 C. (The charge of an electron. ) The modern value is −1.602176462 x 10 -19 C. (Often written in “atomic units” as charge = −1).

9. 2-9 CHEM 100, FALL 2011 LA TECH Millikan’s Experiment

10. 2-10 CHEM 100, FALL 2011 LA TECH Mass of an Electron The experiments by Thomson and Millikan gave the mass/charge ratio and charge of an e −. The modern value is: m e = 9.10938188 x 10 -28 g = (−1.60 x 10 -19 C)(−5.60 x 10 -9 g/C) = 8.96 x 10 -28 g m e = charge x mass charge

11. 2-11 CHEM 100, FALL 2011 LA TECH Protons Atoms become positively charged when e - are lost. Implies a positively charged fundamental particle. Hydrogen ions had the lowest mass. protons – Hydrogen nuclei were assumed to have “unit mass” common to all atoms and were called protons. Modern science: mp = 1.67262158 x 10 -24 g – mp is approximately 1800 times larger than me. – I’ll use shorthand: p + = proton. – Charge equal, but of opposite sign, to the electron. – Charge = +1.602176462 x 10 -19 C (+1 in atomic units).

12. 2-12 CHEM 100, FALL 2011 LA TECH Nuclear Atom How were these particles (p + and e - ) arranged? Thompson thought it was a ball of uniform positive charge, with small negative dots (e - ) stuck in it. The “plum-pudding” model.

13. 2-13 CHEM 100, FALL 2011 LA TECH The Nucleus 1910 Rutherford fired α-particles at thin metal foils. He expected them to pass through the foil. But … But … a few α’s were deflected through large angles. Some came almost straight back! α particles Rutherford “…it was about as credible as if you had fired a 15-inch shell at a piece of paper and it came back and hit you.”

14. 2-14 CHEM 100, FALL 2011 LA TECH The Nucleus Explanation? nucleus Most of the mass (and all the positive charge) is concentrated in a tiny core – the nucleus. – approximately 10,000 times smaller than entire atom. The rest of the volume filled by the electrons. α particles

15. 2-15 CHEM 100, FALL 2011 LA TECH Rutherford estimated that the charge of the nucleus of an atom was about one half of the atomic mass. Moseley, while working for Rutherford, developed a more accurate measurement. While working with cathode rays on metal targets, he measured the wavelength of the X-rays produced. He found that a direct relationship exists between the metal’s atomic number and the square root of the frequency. Determination of nuclear charge

16. 2-16 CHEM 100, FALL 2011 LA TECH Moseley, Henry & Gwyn Jeffreys 1887–1915, English physicist. studied the relations among x-ray spectra of different elements. concluded that the atomic number is equal to the charge on the nucleus based on the x-ray spectra emitted by the element. explained discrepancies in Mendeleev’s Periodic Law. Discovery of Protons and Atomic Number

17. 2-17 CHEM 100, FALL 2011 LA TECH Moseley concluded that the charge of the nucleus was an integer. Further, it was the same as the number of electrical units (electrons) but of opposite charge. Moseley concluded that the charge of the nucleus was an integer. Further, it was the same as the number of electrical units (electrons) but of opposite charge. Atomic number X-Ray Frequency 1/2 Determination of nuclear charge

18. 2-18 CHEM 100, FALL 2011 LA TECH 19321932 Chadwick observed that when beryllium-9 was exposed to alpha particles, particles with the same mass as protons but no charge were given off. These were called neutrons and are present in all atoms except hydrogen-1. They contribute to the force that holds the nucleus together and reduce the repulsive force between positively charged protons. Mass very similar to protons is 0.1% larger). m n = 1.674928716 x 10 -24 g. Discovery of neutrons

19. 2-19 CHEM 100, FALL 2011 LA TECH Summary of Subatomic Particles ParticleChargeMass (g)Mass (amu) Proton Neutron Electron +1.6 x 10 -19 C zero -1. 6 x 10 -19 C 1.7 x 10 -24 g 9.1 x 10 -28 g 1.0073 1.0087 5. 5x 10 -4 Remember: Atoms are usually electrically neutral, Indicating equal numbers of protons and electrons!

20. 2-20 CHEM 100, FALL 2011 LA TECH Structure of the Atom Atoms are composed of subatomic particles: Nucleus Nucleus – Made of protons and neutrons. – Contains most of the mass of the atom. – Small (~10,000 times smaller than the entire atom). – Positive (each p + has unit positive charge). – At the center of an atom. – Very small light particles that surround the nucleus. – Occupy most of an atom’s volume. – Each has unit negative charge. Atoms are neutral. Number of e − = Number of p + Electrons Electrons

21. 2-21 CHEM 100, FALL 2011 LA TECH Sizes of Atoms and Units Atoms are very small – we need to consider very small numbers. A teaspoon of water contains 3x as many atoms as there are teaspoons of water in the Atlantic Ocean! It would be impractical to describe nanoscale objects in pounds and inches. – We need much smaller scales. Need to use units in use around the world: – The metric system. – The SI system (Systeme International) - derived from the metric system.

22. 2-22 CHEM 100, FALL 2011 LA TECH Atomic number, Z Atomic number, Z The number of protons in the nucleus The number of electrons in a neutral atom The integer on the periodic table for each element

23. 2-23 CHEM 100, FALL 2011 LA TECH Structure of the Atom electrons found in electron cloud relative charge of -- 1.602 1773 x 10 -19 C relative mass of 0.00055 amu protons found in nucleus relative charge of +1 relative mass of 1.0073 amuneutrons found in nucleus neutral charge relative mass of 1.0087 amu

24. 2-24 CHEM 100, FALL 2011 LA TECH Relative size of atom and atomic nucleus

25. 2-25 CHEM 100, FALL 2011 LA TECH Scanning Tunneling Microscope

26. 2-26 CHEM 100, FALL 2011 LA TECH Ions Charged single atom Charged cluster of atoms Cations : positive ions Anions : negative ions Ionic compounds: combination of cations and anions with zero net charge

27. 2-27 CHEM 100, FALL 2011 LA TECH Nuclear Notation X = atomic symbol A = mass number Z = atomic number C-12, carbon-12 X A C 12 Z X A 6 C 12

28. 2-28 CHEM 100, FALL 2011 LA TECH Mass Number, A integer representing the approximate mass of an atom equal to the sum of the number of protons and neutrons in the nucleus

29. 2-29 CHEM 100, FALL 2011 LA TECH The atomic symbol & isotopes Isotopic symbol: atomic symbol showing atomic number (Z) and mass number (A) Determine the number of protons, neutrons and electrons in each of the following. P3115 Ba138 56 56 U238 92 922+

30. 2-30 CHEM 100, FALL 2011 LA TECH Isotopes *Atoms of the same element but having different masses. *All isotopes of an element have same atomic number * Each isotope has a different number of neutrons. Isotopes of hydrogenHHH Isotopes of carbon CCC 1111 2121 3131 12 6 13 6 14 6

31. 2-31 CHEM 100, FALL 2011 LA TECH Isotopes Most elements occur in nature as a mixture of isotopes. ElementNumber of stable isotopesElementNumber of stable isotopes H 2H 2 C 2C 2 O 3O 3 Fe 4Fe 4 Sn 10Sn 10 This is one reason why atomic masses are not whole numbers. They are based on averages.

32. 2-32 CHEM 100, FALL 2011 LA TECH Atoms are composed of _____, _____ and ______. Atoms are composed of _____, _____ and ______. Almost all of the mass of an atom comes from the ______ and ______. Almost all of the mass of an atom comes from the ______ and ______. All atoms of the same element will have the same number of ______. All atoms of the same element will have the same number of ______. The number of _______ may vary in isotopes of an element. The number of _______ may vary in isotopes of an element. Most elements exist as a mixture of _______. Most elements exist as a mixture of _______. Isotopes

33. 2-33 CHEM 100, FALL 2011 LA TECH Measurements or observations are made using our physical senses or using scientific instruments. 1) Qualitative measurements. Changes that cannot be expressed in terms of a number. 2) Quantitative measurements. expressed in terms of a number and an unit. Measurement

34. 2-34 CHEM 100, FALL 2011 LA TECH Scientific Measurement

35. 2-35 CHEM 100, FALL 2011 LA TECH Units

36. 2-36 CHEM 100, FALL 2011 LA TECH SI units SI - System International Systematic subset of the metric system. Only uses certain metric units. Mass kilogramsMass kilograms LengthmetersLengthmeters TimesecondsTimeseconds TemperatureKelvinTemperatureKelvin AmountmoleAmountmole Other SI units are derived from SI base units.

37. 2-37 CHEM 100, FALL 2011 LA TECH Metric prefixes Changing the prefix alters the size of a unit. Prefix Symbol Factor mega M10 6 1 000 000 kilo k10 3 1 000 hecto h10 2 100 deka da10 1 10 base -10 0 1 deci d10 -1 0.1 centi c10 -2 0.01 milli m10 -3 0.001 micro  10 -6 0.0000001 nanon 10 -9 0.000000000001

38. 2-38 CHEM 100, FALL 2011 LA TECH Metric Prefixes

39. 2-39 CHEM 100, FALL 2011 LA TECH 5.0 lb Unit Conversions Example How many grams of sugar are there in a 5.0 lb bag of sugar? Look up conversion factor: 1 lb = 453. g = 2265 g x 453. g 1 lb = 2.3 x 10 3 g = 2.3 kg Too many digits for the final answer!

40. 2-40 CHEM 100, FALL 2011 LA TECH Metric Units: Metric System Prefix Factor Example megaM10 6 1 megaton = 1 x 10 6 tons kilok10 3 1 kilometer (km) = 1 x 10 3 meter (m) decid10 -1 1 deciliter (dL) = 1 x 10 -1 liter (L) centic10 -2 1 centimeter (cm) = 1 x 10 -2 m millim10 -3 1 milligram (mg) = 1 x 10 -3 gram (g) microμ 10 -6 1 micrometer (μm) = 1 x 10 -6 m nanon10 -9 1 nanogram (ng) = 1 x 10 -9 g picop10 -12 1 picometer (pm) = 1 x 10 -12 m femtof10 -15 1 femtogram (fg) = 1 x 10 -15 g A decimal system. Prefixes multiply or divide a unit by multiples of ten.

41. 2-41 CHEM 100, FALL 2011 LA TECH Example. Metric Conversion How many milligrams are in a kilogram? 1 kg=1000 g 1 g =1000 mg 1 kg x 1000 x 1000 = 1 000 000 mg kg g mg g

42. 2-42 CHEM 100, FALL 2011 LA TECH Metric conversion factors: 1 pm = 1 x 10 -12 m 1 cm= 1 x 10 -2 m Metric Units Example How many copper atoms lie across the diameter of a penny? A penny has a diameter of 1.90 cm, and a copper atom has a diameter of 256 pm.

43. 2-43 CHEM 100, FALL 2011 LA TECH x 1 x 10 -2 m 1 cm = 7.42 x 10 7 Cu atoms 1 pm 1 x 10 -12 m x Metric Units Convert the diameter into the same units as a Cu atom: 1.90 cm = 1.90 x 10 10 pm Calculate the number of atoms across the diameter: 1.90 x 10 10 pm x 1 Cu atom 256 pm

44. 2-44 CHEM 100, FALL 2011 LA TECH Common Unit Equalities Length Length1 kilometer= 1000 m = 0.62137 mile 1 inch= 2.54 cm (exactly) 1 angstrom (Å)= 1 x 10 -10 m Volume Volume1 liter (L) = 1 x 10 -3 m 3 = 1000 cm 3 = 1000 mL = 1.056710 quarts 1 gallon= 4 quarts = 8 pints Mass Mass1 amu= 1.6606 x 10 -24 g 1 pound= 453.59237 g = 16 ounces 1 ton (metric)= 1000 kg 1 ton (US)= 2000 pounds

45. 2-45 CHEM 100, FALL 2011 LA TECH 165 mg dL Unit Conversions A patient’s blood cholesterol level measured 165 mg/dL. Express this value in g/L Determine the conversion relationships: 1 mg = 1 x 10 -3 g 1 dL = 1 x 10 -1 L x 1 x10 -3 g 1 mg = 1.65 g/L x 1 dL 1 x10 -1 L

46. 2-46 CHEM 100, FALL 2011 LA TECH Uncertainty and Significant Figures All measurements involve some uncertainty. plus Scientists write down all the digits that have no uncertainty plus one additional uncertain digit. If an object is reported to have a mass = 6.3492 g, the last digit (“2”) is uncertain ( it is probably close to 2, but may be 4, 1 …). significant figures There are five significant figures in this number. All the digits are meaningful.

47. 2-47 CHEM 100, FALL 2011 LA TECH Uncertainty and Significant Figures To find the number of significant figures: Read a number from left to right and count all digits, starting with the first non-zero digit. All digits are significant except those zeros that are used to position a decimal point (“placeholders”). 0.00034050 5 sig. figs. Scientific Notation (3.4050 x 10 -4 ) Scientific Notation (3.4050 x 10 -4 ) placeholders significant

48. 2-48 CHEM 100, FALL 2011 LA TECH Uncertainty and Significant Figures Number Sig. figs.Comment 2.123 4.5004 The zeros are not placeholders. They are significant. 0.0025414 The zeros are placeholders (not significant). 0.001003 Only the last two zeros are significant. 500 1, 2, 3 ? Ambiguous. If a number lacks a decimal point the zeros may be placeholders or may be significant. 500.3 Adding a decimal point is one way to show that the zeros are significant. 5.0 x 10 2 2 No ambiguity. Examples

49. 2-49 CHEM 100, FALL 2011 LA TECH adp = 4 adp = 3 Significant Figures The answer you report in a problem should only include significant digits. Addition and subtraction Find the number of digits after the decimal point (adp) in each number. answer adp = smallest input adp. ExampleAdd:17.245 + 0.1001 + 0.100117.3451 3 Rounds to: 17.345(adp = 3)

50. 2-50 CHEM 100, FALL 2011 LA TECH Significant Figures adp = 2 adp = 4Example Subtract 6.72 x 10 -1 from 5.00 x 10 1 Write the numbers down with the same power of 10: 5.00 x 10 1 5.00 x 10 1 – 0.0672 x 10 1 – 0.0672 x 10 1 4.9328 x 10 1 Rounds to:4.93 x 10 1 adp = 2

51. 2-51 CHEM 100, FALL 2011 LA TECH sig. fig. = 4 sig. fig. = 5 Significant Figures Multiplication and Division Find the number of significant figures (sig. fig.) in each number. Answer has sig. fig = smallest input sig. fig. Example Multiply 17.425 and 0.1001 17.245 x 0.1001 x 0.10011.7262245 Rounds to:1.726 sig. fig. = 4 Example Multiply 2.346 x 12.1 x 500.99 Rounds to: 1.42 x 10 4 (3 sig. fig.) = 14,221.402734

52. 2-52 CHEM 100, FALL 2011 LA TECH Consider rounding 37.663147 to 3 significant figures.Rounding Look at the 1 st non-significant digit (the digit after the last one retained). If it: is > 5, round the last retained digit up by 1. is < 5, make no change. equals 5, and the 2 nd non-significant digit is: absent, round the last retained digit up by 1. odd, round the last retained digit up by 1. even, make no change. last retained digit 1 st non-significant digit It rounds up to 37.7 2 nd non-significant digit

53. 2-53 CHEM 100, FALL 2011 LA TECH RoundingExamples Round the following numbers to 3 significant figures: 1 st non-sig.2 nd non-sig.Rounded Number digit digit Number 3 2.123 2.123- 2.12 72 51.372 51.372 51.372 51.4 5 131.5131.5- 132. 52 24.752 24.752 24.752 24.7 51 24.751 24.751 24.751 24.8 4 0.067440.06744- 0.0674

54. 2-54 CHEM 100, FALL 2011 LA TECH How many digits are significant? Significant Figures and Rounding Example Perform the following calculation and report the answer with the correct number of significant figures: 99.12444 – 6.321 27.5256 = 92.80344 27.5256 = 3.37153195571 = 3.3715 (5 sig. figs.) adp = 5adp = 3 92.803 is the significant result (adp = 3; 5 sig. figs.) 6 sig. figs.

55. 2-55 CHEM 100, FALL 2011 LA TECH Significant Figures and Rounding To avoid rounding errors carry 1 additional digit through a calculation. round the final answer to the correct number of places.Remember Exact conversion factors like (100 cm / 1 m) or (2H / 1 H 2 O) have an infinite number of significant figures.

56. 2-56 CHEM 100, FALL 2011 LA TECH Problem Solving by Factor Label Method State question in mathematical form Set equal to piece of data specific to the problem Use conversion factors to convert units of data specific to problem to units sought in answer Other names used Unit Conversion Method or dimensional (Unit) Analysis

57. 2-57 CHEM 100, FALL 2011 LA TECH Exact Numbers conversion factors should never limit the number of significant figures reported in answer 12 inches = 1 foot

58. 2-58 CHEM 100, FALL 2011 LA TECH Speed of light is 3.00 x 10 8 m s -1. Convert the speed of light to miles per year (1 mile = 1.61 km).Calculation

59. 2-59 CHEM 100, FALL 2011 LA TECH Temperature Scales:FahrenheitCelsiusKelvin absolute scale using Celsius size degree

60. 2-60 CHEM 100, FALL 2011 LA TECH Three Temperature Scales FahrenheitCelsiusKelvin Boiling Point of Water 212 100373 Normal Body Temp. Melting Point of Water Absolute Zero - 2730- 459 98.637310 32 0 273

61. 2-61 CHEM 100, FALL 2011 LA TECH Temperature Conversions o F -- > o C ; C = 5/9 (F - 32) o C -- > o F ; F =9/5 C + 32 o C -- > K ; K = C + 273.15 Human body temperature is 98.6 o F. Convert this temperature to o C and K scale o C = 5/9 (98.6 - 32) = 5/9 (66.6) = 37.0 o C--> K = 37.0 o C +273.15 = 310.2 K

62. 2-62 CHEM 100, FALL 2011 LA TECH Measuring volume Volume - the amount of space that an object occupies. The base metric unit is the liter (L). The common unit used in the lab is the milliliter (mL). One milliliter is exactly equal to one cm 3. The derived SI unit for volume is the m 3 which is too large for convenient use.

63. 2-63 CHEM 100, FALL 2011 LA TECH Density Density is an intensive property of a substance based on two extensive properties. Common units are g / cm 3 or g / mL. »g / cm 3 g / cm 3 Air 0.0013Bone1.7 - 2.0 Water 1.0Urine1.01 - 1.03 Gold19.3Gasoline0.66 - 0.69 Density = Mass Volume cm 3 = mL

64. 2-64 CHEM 100, FALL 2011 LA TECH Density Calculations Equation method: Density = mass ÷ volume; d = m/v Factor Label method: 14.2 g -- > ? cm3 conversion factor? 2.70 g 1 cm 3 2.70 g 1 cm 3 -------- or ------ -------- or ------ 1 cm 3 2.70 g 1 cm 3 2.70 g 14.2 g x 1 cm 3 --------------------- = 5.26 cm 3 2.70 g 2.70 g

65. 2-65 CHEM 100, FALL 2011 LA TECH Specific gravity measurement Hydrometer Float height will be based on Specific Gravity = density of substance density of reference Specific Gravity is unitless. Reference is commonly water at 4 o C.

66. 2-66 CHEM 100, FALL 2011 LA TECH Average atomic masses Most elements exits as a mixture of isotopes. Most elements exits as a mixture of isotopes. Each isotope may be present in different amounts. Each isotope may be present in different amounts. The masses listed in the periodic table reflect the world-wide average for each isotope. The masses listed in the periodic table reflect the world-wide average for each isotope. One can calculate the average atomic weight (AAM) of an element if the abundance of each isotope for that element is known. One can calculate the average atomic weight (AAM) of an element if the abundance of each isotope for that element is known.

67. 2-67 CHEM 100, FALL 2011 LA TECH Masses of Atoms Carbon-12 Scale Masses of the atoms are compared to the mass of C-12 isotope having a mass of 12.0000 amu Atomic mass units (amu)

68. 2-68 CHEM 100, FALL 2011 LA TECH Mass Spectrometer

69. 2-69 CHEM 100, FALL 2011 LA TECH Mass Spectrum of Neon AAM(Ar) = [(90 x 20) + (10 x 22)] / 100 = 20.20

70. 2-70 CHEM 100, FALL 2011 LA TECH Atomic Masses and Isotopic Abundances natural average atomic masses =  [(atomic mass of isotope)  (fractional isotopic abundance)]

71. 2-71 CHEM 100, FALL 2011 LA TECH How do you calculate average Atomic Mass? M a x a + M b x b ------------------------ = AAM 100 100 M a = mass of isotope a M b = mass of isotope b a = percent abundance of a a = percent abundance of a b = percent abundance of b b = percent abundance of b AAM = Average atomic mass (Reported on the Periodic Table) on the Periodic Table)

72. 2-72 CHEM 100, FALL 2011 LA TECH Ma x a + Mb x b = AAM Ma = mass of isotope a Mb = mass of isotope b a = fractional abundance of a b = fractional abundance of b AAM = Average atomic mass (Reported on the Periodic Table) How do you calculate average Atomic Mass?

73. 2-73 CHEM 100, FALL 2011 LA TECH Average atomic masses Example. Silicon exists as a mixture of three isotopes. Determine it’s average atomic mass based on the following data. Isotope Mass (u) Abundance 28 Si27.976 926592.23 % 29 Si28.976 4947 4.67 % 30 Si29.973 7702 3.10 %

74. 2-74 CHEM 100, FALL 2011 LA TECH Gallium in nature consists of two isotopes, gallium-69, with a mass of 69.926 amu and a fractional abundance of 0.601; and gallium-71, with a mass of 70.925 amu and a fractional abundance of 0.399. Calculate the weighted average atomic mass of gallium. 1) M a x a + M b x b = AAM M a x a(%) + M b x b(%) 2) ----------------------------------- = AAM 100 Calculation

75. 2-75 CHEM 100, FALL 2011 LA TECH M a ( 69 Ga ) =68.926 u, a = percent abundance of 69 Ga = 0.601 x 100 M b ( 71 Ga ) = 70.925 u, b = percent abundance of 71 Ga = 0.339 x 10 We can obtain an equation with one unknown, AAM. AAM = 68.926x(0.601 x 100)+70.925 x(0.339x100) 100 100 AAM (Ga) = 4142.5 + 2829.9 100 100 AAM (Ga) = 6972.3 = 69.723 100 100 AAM (Ga) = 69.723 u (amu) AAM Calculation

76. 2-76 CHEM 100, FALL 2011 LA TECH The Mole a unit of measurement, quantity of matter present Avogadro’s Number 6.022  10 23 particles Latin for “pile”

77. 2-77 CHEM 100, FALL 2011 LA TECH Molar Mass Sum atomic masses (amu or g/mol) represented by formula atomic masses  gaw (g/mol) molar mass  MM

78. 2-78 CHEM 100, FALL 2011 LA TECH Example How many grams of Cu are there in 5.67 mol Cu? #g Cu = (5.67 mol)(63.546g/mol) = 360. g = 360. g Atomic mass of Cu

79. 2-79 CHEM 100, FALL 2011 LA TECH Example Calculate the number of boron atoms in 1.000g sample of the element. #B atoms = (1.000g)(1mol / 10.81g)  (6.022  10 23 atoms/mol)  (6.022  10 23 atoms/mol) = 5.571  10 22 B atoms = 5.571  10 22 B atoms

80. 2-80 CHEM 100, FALL 2011 LA TECH Example How many moles of silicon, S, are in 30.5g of S? #mol Si = (30.5g)(1 mol/32.06g) = 0.951 mol Si = 0.951 mol Si

81. 2-81 CHEM 100, FALL 2011 LA TECH Example What is the molar mass of methanol, CH 3 OH? MM = 1(gaw) C + (3 + 1)(gaw) H + 1(gaw) O = 1(12.011) C + 4(1.00794) H + 1(15.9994) O = 22.042 g/mol

82. 2-82 CHEM 100, FALL 2011 LA TECH Example How many moles of carbon dioxide molecules are there in 6.45g of carbon dioxide? MM = 1(gaw) C + 2(gaw) O = 44.01 g/mol #mol CO 2 = (6.45g)(1 mol/44.01g) = 0. 147 mol = 0. 147 mol

83. 2-83 CHEM 100, FALL 2011 LA TECH Periodic Table Periodic table is an arrangement of all known element according to their atomic number and chemical properties.

84. 2-84 CHEM 100, FALL 2011 LA TECH Development of Periodic Table Newlands - English Scientist 1864 – Law of Octaves – every 8th element has similar properties

85. 2-85 CHEM 100, FALL 2011 LA TECH Who is Dmitri Mendeleev? Mendeleev, Dmitri (1834-1907): Russian chemist Mendeleev, Dmitri (1834-1907): Russian chemist Mendeleev is best known for Mendeleev is best known for his work on the periodic table; arranging the 63 known elements into a Periodic Table based on Atomic Mass

86. 2-86 CHEM 100, FALL 2011 LA TECH Mendeleev’s Periodic Table the elements are arranged according to increasing atomic weights Missing elements: 44, 68, 72, & 100 amu

87. 2-87 CHEM 100, FALL 2011 LA TECH Dimitri Mendeleev created this, the original, periodic table.

88. 2-88 CHEM 100, FALL 2011 LA TECH Predicted Properties of Ekasilicon

89. 2-89 CHEM 100, FALL 2011 LA TECH Modern Periodic Table the elements are arranged according to increasing atomic numbers

90. 2-90 CHEM 100, FALL 2011 LA TECH Organization of Periodic Table Period Period – horizontal row Group –vertical column

91. 2-91 CHEM 100, FALL 2011 LA TECH Modern periodic table H Li Na Cs Rb K TlHgAuHfLuBa Fr PtIrOsReWTa He RnAtPoBiPb Be Mg Sr Ca CdAgZrYPdRhRuTcMoNb LrRa ZnCuTiScNiCoFeMnCrV InXeITeSbSn GaKrBrSeAsGe AlArClSPSi BNeFONC 1 213 1 4 15 1 6 17 18 I A II A III A IV A V A VI A VIIA 0 3 4 5 6 7 8 9 10 11 12 III B IVB V B VIB VIIB VIII B IB IIB 12345671234567 Gd Cm Tb Bk Sm Pu Eu Am Nd U Pm Np Ce Th Pr Pa Yb No La Ac Er Fm Tm Md Dy Cf Ho Es * + + *

92. 2-92 CHEM 100, FALL 2011 LA TECH Information that may be in the table Ag 107.87 Silver 47 Atomic number Name of the element Elemental Symbol Average Atomic mass

93. 2-93 CHEM 100, FALL 2011 LA TECH Vertical columns- groups,families Horizontal columns- periods Elements in a group have similar chemical properties Group IA - alkali metal: Li, Na, K Rb, Cs, Fr Group IIA- alkaline earth metals: Be, Mg, Ca, Sr, Ba, Ra Group VIIA - Halogens: Cl, Br, I, At Group 0 - Noble gases: He, Ne, Ar, Kr, Xe, Rn

94. 2-94 CHEM 100, FALL 2011 LA TECH A group or family He Rn XeI KrBrSe ArClS NeFO P NC H Li Na Cs Rb K TlHgAuHfLuBa Fr PtIrOsReWTaPoBiPb Be Mg Sr Ca CdAgZrYPdRhRuTcMoNb LrRa ZnCuTiScNiCoFeMnCrV InSbSn GaGe Al Gd Cm Tb Bk Sm Pu Eu Am Nd U Pm Np Ce Th Pr Pa Yb No La Ac Er Fm Tm Md Dy Cf Ho Es At Te As Si B I A II A III A IV A V A VI A VIIA 0 III B IVB V B VIB VIIB VIII IB IIB Groups are assigned Roman numerals with an A or B Groups are assigned Roman numerals with an A or B

95. 2-95 CHEM 100, FALL 2011 LA TECH A row or period He Rn XeI KrBrSe ArClS NeFO P NC H Li Na Cs Rb K TlHgAuHfLuBa Fr PtIrOsReWTaPoBiPb Be Mg Sr Ca CdAgZrYPdRhRuTcMoNb LrRa ZnCuTiScNiCoFeMnCrV InSbSn GaGe Al Gd Cm Tb Bk Sm Pu Eu Am Nd U Pm Np Ce Th Pr Pa Yb No La Ac Er Fm Tm Md Dy Cf Ho Es At Te As Si B 12345671234567 Periods are assigned numbers Periods are assigned numbers

96. 2-96 CHEM 100, FALL 2011 LA TECH Elemental states at room temperature He Rn Xe I Kr BrSe Ar Cl S Ne FO P N C H Li Na Cs Rb K TlHgAuHfLuBa Fr PtIrOsReWTaPoBiPb Be Mg Sr Ca CdAgZrYPdRhRuTcMoNb LrRa ZnCuTiScNiCoFeMnCrV InSbSn GaGe Al Gd Cm Tb Bk Sm Pu Eu Am Nd U Pm Np Ce Th Pr Pa Yb No La Ac Er Fm Tm Md Dy Cf Ho Es At Te As Si B Solid Liquid Gas * + * +

97. 2-97 CHEM 100, FALL 2011 LA TECH The known elements 118 elements are currently known 89 are metals 31 are radioactive 22 are synthetic (all radioactive) 11 occur as gases 2 occur as liquids Let’s take a look at them on the table.

98. 2-98 CHEM 100, FALL 2011 LA TECH Periodic Table of the Elements

99. 2-99 CHEM 100, FALL 2011 LA TECH Family Names Group IAalkali metals Group IIAalkaline earth metals Group VIIAhalogens Group VIIIAnoble gases transition metals inner transition metals lanthanum seriesrare earths actinium seriestrans-uranium series

100. 2- 100 CHEM 100, FALL 2011 LA TECH What are these? Transition Metals Actinides Lanthanides Semimetals or Metalloids Ionic Charges Poly atomic ions and their charges