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Chem 106, Prof. J.T. Spencer 1 CHE 106: General Chemistry u CHAPTER TWO Copyright © James T. Spencer 1995 - 1999 All Rights Reserved.

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Presentation on theme: "Chem 106, Prof. J.T. Spencer 1 CHE 106: General Chemistry u CHAPTER TWO Copyright © James T. Spencer 1995 - 1999 All Rights Reserved."— Presentation transcript:

1 Chem 106, Prof. J.T. Spencer 1 CHE 106: General Chemistry u CHAPTER TWO Copyright © James T. Spencer All Rights Reserved

2 Chem 106, Prof. J.T. Spencer 2 u What is Chemistry Chapter 2: Atoms, Molecules and Ions Chapt. 2.1 Magic Logic

3 Chem 106, Prof. J.T. Spencer 3 u Science: Atomic Theory The strength of a science is that its conclusions are derived by logical arguments from facts that result from well-designed experiments. Science has produced a picture of the microscopic structure of the atom so detailed and subtle of something so far removed from our immediate experience that it is difficult to see how its many features were constructed. This is because so many experiments have contributed to our ideas about the atom. –“ The strength of a science is that its conclusions are derived by logical arguments from facts that result from well-designed experiments. Science has produced a picture of the microscopic structure of the atom so detailed and subtle of something so far removed from our immediate experience that it is difficult to see how its many features were constructed. This is because so many experiments have contributed to our ideas about the atom. ” B. Mahan from University Chemistry Atoms, Molecules and Ions Chapt. 2.1

4 Chem 106, Prof. J.T. Spencer 4 STM image showing single- atom defect in iodine adsorbate lattice on platinum. “Seeing “Atoms

5 Chem 106, Prof. J.T. Spencer 5 Macroscopic Microscopic Substances Atomic theory Mixtures Physical Properties and Changes u Science: Atomic Theory –from a fundamental understanding of the macroscopic behavior of substances comes an understanding the microscopic behavior of atoms and molecules (Baseball rules from Baseball Game?) Atoms, Molecules and Ions Chapt. 2.1 Question: Can matter be infinitely divided? Most Greek Philosophers - Yes Democritus (460 BC) and John Dalton (1800s) - No (“atomos”means indivisible”)

6 Chem 106, Prof. J.T. Spencer 6 Atoms, Molecules and Ions Chapt. 2.1 u History of Atomic Theory and Scientific Inquiry –Aristotle - “metaphysics”, thought experiments and no experimental observations necessary to substantiate ideas. –Archimedes ( BC) - Scientific Method, determined composition of the King of Syracuse’s crown by measuring density through water displacement. –Roger Bacon ( ) - Experimental Science “ It is the credo of free men - the opportunity to try, the privilege to err, the courage to experiment anew....experiment, experiment, ever experiment”.

7 Chem 106, Prof. J.T. Spencer 7 u All of the sciences (epistêmai, literally "knowledges") can be divided into three branches: theoretical, practical, and productive. theoretical sciences, such as theology, mathematics, and the natural sciences, aim at truth and are pursued for their own sake. u All of the sciences (epistêmai, literally "knowledges") can be divided into three branches: theoretical, practical, and productive. Whereas practical sciences, such as ethics and politics, are concerned with human action, and productive sciences with making things, theoretical sciences, such as theology, mathematics, and the natural sciences, aim at truth and are pursued for their own sake. Aristotle ( BC)

8 Chem 106, Prof. J.T. Spencer 8 u Archimedes was a native of Syracuse (not NY). Stories from Plutarch, Livy, and others describe machines invented by Archimedes for the defence of Syracuse (These include the catapult, the compound pulley and a burning-mirror). u Archimedes discovered fundamental theorems concerning the centre of gravity of plane figures and solids. His most famous theorem gives the weight of a body immersed in a liquid, called Archimedes' principal. Archimedes ( BC) u His methods anticipated integral calculus 2,000 years before Newton and Leibniz.

9 Chem 106, Prof. J.T. Spencer 9 Archimedes ( BC)

10 Chem 106, Prof. J.T. Spencer 10 Suspecting that a goldsmith might have replaced some of the gold by silver in making a crown, Hiero II, the king of Syracuse, asked Archimedes to determine whether the wreath was pure gold. The wreath could not be harmed since it was a holy object. The solution which occurred when he stepped into his bath and caused it to overflow was to put a weight of gold equal to the crown, and known to be pure, into a bowl which was filled with water to the brim. Then the gold would be removed and the king's crown put in, in its place. An alloy of lighter silver would increase the bulk of the crown and cause the bowl to overflow. Equal Weight of Gold Crown Displaced More Water Archimedes ( BC) Pure Gold?

11 Chem 106, Prof. J.T. Spencer 11 Greek Philosophers u Democratus - First to say that all matter is NOT infinately divisible. [But the Greeks did not test their ideas] u Alchemy - Pseudoscience by fakes and mystics devoted to turning base metals to gold BUT they did make (by accident) many ground breaking discoveries of nature (chemical reactions). Earth Air Fire Water Greek “Elements”

12 Chem 106, Prof. J.T. Spencer 12 Scientific Measurement Robert Boyle - Robert Boyle ( ) was born in Ireland. He became especially interested in experiments involving air and developed an air pump with which he produced evacuated cylinders. He used these cylinders to show that a feather and a lump of lead fall at the same rate in the absence of air resistance. In his book “The Sceptical Chemist” (1661), Boyle urged that the ancient view of elements as mystical substances should be abandoned and that an element should instead be defined as anything that cannot be broken down into simpler substances.

13 Chem 106, Prof. J.T. Spencer 13 Scientific Measurement u Antoine Lavoisier ( ) - Furthered measurement as basis for scientific reasoning. –“Je Veux Parler Des Faits” –“Je Veux Parler Des Faits” - Do Not Rely Upon Speculation But Build Upon Facts. More on Lavoisier on Next Slide

14 Chem 106, Prof. J.T. Spencer 14 Antoine Lavoisier Antoine Lavoisier was born in Paris, and although Lavoisier's father wanted him to be a lawyer, Lavoisier was fascinated by science. From the beginning of his scientific career, Lavoisier recognized the importance of accurate measurements. He wrote the first modern chemistry (1789) textbook so that it is not surprising that Lavoisier is often called the father of modern chemistry. To help support his scientific work, Lavoisier invested in a private tax-collecting firm and married the daughter of one of the company executives. Guillotined for his tax work in 1794.

15 Chem 106, Prof. J.T. Spencer 15 Atoms, Molecules and Ions Chapt. 2.1 pure water evaporate out water from dust sealed container “earth” alchemists said that the water was “transmuted” to earth Lavoisier showed that the amount of “earth” found at the end of the experiment was equal to the weight the container lost, therefore, the water was not “transmuted” to earth. Earth FireWater Alchemy u History Atomic Theory and Scientific Inquiry –Lavoisier ( ) - founder of “modern chemistry”, not to rely on speculation but to build upon facts, ended the “time of alchemy”. Law of Conservation of Mass

16 Chem 106, Prof. J.T. Spencer 16 Scientific Method Chapt. 2.1 Observations and Experiments Patterns and Trends Form and test hypothesis Theory

17 Chem 106, Prof. J.T. Spencer 17 John Dalton ( ) John Dalton ( ), an Englishman, began teaching school when he was 12. He was fascinated with meteorology (keeping daily weather records for 46 years), which led to an interest in gases and their components, atoms. He switched to chemistry when he saw applications in chemistry for his ideas about the atmosphere. He proposed the Atomic Theory in Dalton was a humble man with several apparent handicaps: he was poor; he was not articulate; he was not a skilled experimentalist, and he was color-blind (a terrible problem for a chemist). In spite of these disadvantages he did great things.

18 Chem 106, Prof. J.T. Spencer 18 u John Dalton’s Atomic Theory –Designed a theory to account for a variety of experimental observations: –Each element is composed of extremely small particles (called atoms). –All atoms of a given element are identical (therefore, atoms of different elements are different and have different properties). Atomic Theory Chapt. 2.1

19 Chem 106, Prof. J.T. Spencer 19 u John Dalton’s Atomic Theory –Atoms of an element are not changed into different types of atoms by chemical reactions and atoms are neither created nor destroyed in chemical reactions. –Compounds are formed when atoms combine and a given compound always has the same relative number and kind of atoms. Atomic Theory (Continued) Chapt. 2.1

20 Chem 106, Prof. J.T. Spencer 20 u Dalton’s Atomic Theory –Atoms are the building blocks: –Elements –Elements are composed of only one kind of atom. –Compounds –Compounds are made by mixing atoms in definite proportions –Mixtures –Mixtures do not involve the type of “small scale” (but strong) interactions found in Elements and Compounds Atomic Theory Chapt. 2.1

21 Chem 106, Prof. J.T. Spencer 21 u Law of Constant Composition (or Definite Proportion, first proposed by Joseph Proust) : –In any given compound, the relative number and kind of atoms are constant (same proportion of elements by mass). –implies that atoms interact in a specific way when they form a compound. –the elements making up a particular compound combine in the same proportions regardless of the manner in which the compound was prepared. Atomic Theory; Dalton’s Theories Chapt. 2.1

22 Chem 106, Prof. J.T. Spencer 22 u Law of Constant Composition (or Definite Proportion): Atomic Theory; Dalton’s Theories Chapt. 2.1 Copper Carbonate ALWAYS contains 5.3 parts Copper to 4 parts Oxygen and 1 part Carbon (by Weight). Carbon Dioxide ALWAYS contains 1.00 parts Carbon to 2.67 parts Oxygen

23 Chem 106, Prof. J.T. Spencer 23 u Law of Conservation of Mass: –the total amount of material present after a chemical reaction is the same as the amount present before the reaction. Atomic Theory; Dalton’s Theories Chapt. 2.1 Matter (elements, etc...) cannot be created nor destroyed during chemical reactions. Total Mass Before Chemical Reaction Total Mass After Chemical Reaction =

24 Chem 106, Prof. J.T. Spencer 24 u Law of Multiple Proportions: –If two elements form more than one compound, then the ratios of the masses of a second element that combine with 1 g of the first elements can always be reduced to small whole numbers Atomic Theory; Dalton’s Theories Chapt. 2.1 Mass of O Comb. w/ 1 g C I1.33 g II2.66 g III3.99 g

25 Chem 106, Prof. J.T. Spencer 25 u Law of Multiple Proportions: –If two elements form more than one compound, then the ratios of the masses of a second element that combine with 1 g of the first elements can always be reduced to small whole numbers Atomic Theory; Dalton’s Theories Chapt. 2.1 C CCC O OO O O O 1:1 2:1 3:1 Mass of O Comb. w/ 1 g C I1.33 g II2.66 g III3.99 g I II III

26 Chem 106, Prof. J.T. Spencer 26 u Law of Multiple Proportion: Another Example Oxygen combines with hydrogen to form 2 compounds Compound 1 8 grams of oxygen combines with 1 gram of hydrogen [H 2 O] Compound 2 16 grams of oxygen combines with 1 gram of hydrogen [H 2 O 2 ] Atomic Theory; Dalton’s Theories Chapt. 2.1

27 Chem 106, Prof. J.T. Spencer 27 u Law of Multiple Proportion: Yet Another Example Chlorine combined with oxygen to form four binary compounds [A, B, C, D]. Compound Mass of O combined Div. by Compound Mass of O combined Div. by with g Cl with g Cl A g1.00 B g4.00 C g6.00 D g7.00 Atomic Theory; Dalton’s Theories Chapt. 2.1 Allowed Dalton to prepare the first atomic mass table

28 Chem 106, Prof. J.T. Spencer 28 Guy-Lussac Joseph Guy-Lussac ( ) found that (at the same temperatures and pressures): 2 volumes of hydrogen reacts with 1 volume of oxygen to yield 1 volume of water vapor OH Water + = Amedeo Avogadro ( ) proposed that (at the same temperatures and pressures), equal volumes of different gases contain the same number of particles: 2 molecules of H + 1 molecule of O yield 1 molecule of water

29 Chem 106, Prof. J.T. Spencer 29 Experiments in Atomic Theory u Faraday - Electrodeposition u Millikan - Oil Drop Experiment u Roetgen - Radioactivity u Curie - Radioactive Particles u Rutherford - Gold Foil Experiment Dalton’s Laws Set Groundwork for Atomic Theory but Important Experiments Lead to Our Modern Understanding

30 Chem 106, Prof. J.T. Spencer 30 Michael Faraday ( ) Experiments in electro- magnetism, electrical power conversion, etc... Humble scientist rose from very poor background to become one of the most influential of his age. Believed that careful observations were most important. “Try desperately to succeed - and do not hope for success”

31 Chem 106, Prof. J.T. Spencer 31 u Electrical Nature –Michael Faraday (1833) (first ideas about the nature of electricity –The weight of a material deposited at an electrode by a given amount of electricity is always the same. –The weights of various materials deposited by fixed amounts of electricity are proportional to their equivalent weights. [remember equivalent weights] Chapt. 2.1 Atomic Structure electrodes depositionelectrolyte +- ElectrodepositionCell

32 Chem 106, Prof. J.T. Spencer 32 Sir J. J. Thomson British physicist who worked with electrical currents and fields. Appointed Prof. of Physics at Cambridge when he was 27 and Received the Nobel Proze in 1906 for his characterization of the electron.

33 Chem 106, Prof. J.T. Spencer 33 u J. J. Thomson: Cathode Ray Tube (CRT) Experiment – Set up a large electrical potential between a pair of electrodes in a glass tube and an electrical current will flow between the elctrodes. –The current will flow even when all the air is pumped out of the tube. The invisible charge carriers were called “cathode rays”. –Cathode rays travel in straight lines and form a luminious spot when they hit a glass tube. Chapt. 2.1 Atomic Structure (-)(+) Cathode Ray Tube [evacuated glass tube]

34 Chem 106, Prof. J.T. Spencer 34 (-)(+) (-)(+) Electric Field Magnetic Field Chapt. 2.1 Atomic Structure: CRT The cathode rays are deflected by an electric field. The same effect was observed regardless of what gas was used in the discharge tube. Therefore, electricity must be a universal fragment. The cathode rays are deflected by an magnetic field.

35 Chem 106, Prof. J.T. Spencer 35 (-) (+) Electric Field Chapt. 2.1 Electricity: Thomson’s charge to mass Magnetic Field Spotmag field elec. field 1On Off 3Off On 2Off Off On CRT (-) (+)

36 Chem 106, Prof. J.T. Spencer 36 Ee = Electrical FieldHe = Magnetic Field [where e = electric charge (unk) and = velocity] Set up experiment such that; Electrical Field = Magnetic Field Ee = He Ee = He or  E / H Now, turn off the mag. field and measure deflection of beam (  ) Using Newton’s 2nd Law can calculate e/m Thomson’s charge to mass (-) (+) Magnetic Field CRT (-) (+)

37 Chem 106, Prof. J.T. Spencer 37 Thomson’s charge to mass calculated charge to mass ratio (e/m) for electron = 1.76 x 10 8 coulombs/g found; (1) e/m was 1000x greater than for any known ion (2) e/m of independent of gas in tube [Universal Fragment] (3) Not electrified atoms but fragments (called electrons)

38 Chem 106, Prof. J.T. Spencer 38 Nobel Prize, 1923; for his work on the elementary charge of electricity and on the photoelectric effect. Robert Millikan was one of the first American scientists to be recognized in Europe. In 1909 he performed the first of a series of experiments to measure the fundamental charge of an electron, the Millikan Oil Drop Experiment. The value determined by this experiment was used in Bohr's formula for the energy of the Hydrogen line spectrum as a first confirmation of the quantized atom. He named and studied "cosmic rays" as well. Robert Millikan ( )

39 Chem 106, Prof. J.T. Spencer 39 Chapt. 2.1 Electricity: Millikan’s electron mass + - viewer Oil Drop Experiment (1909) atomizer high voltage Goal: to measure the electrical charge on each oil droplet Procedure: measure the velocity of the falling oil drop both with and without the high voltage plates urned on Found: charges were always multiples of 1.60 x C Postulate: charge of one electron was 1.60 x C Ionization by radiation causes the oil to pick up “extra” electrons

40 Chem 106, Prof. J.T. Spencer 40 Chapt. 2.1 Electricity: electron mass charge= e= 1.76 x 10 8 coul g -1 mass m Thomson Millikan Combine and Solve charge = e = 1.60 x coul mass = charge = 1.60 x C = 9.10 x g 1.76 x 108 coul g x 108 C g -1 mass of the electron was 2000x smaller than the lightest atom (hydrogen)

41 Chem 106, Prof. J.T. Spencer 41 Wilhelm Conrad Roentgen Wilhelm Conrad Roentgen was born in Lennep, Germany, on 27 March He obtained a degree in mechanical engineering and, in 1869, was awarded a degree in physics. While working as a professor of physics at Wurzburg University, he made his famous discovery. He called the unknown radiation "X rays," since "X" frequently stands for an unknown quantity in mathematics. His unique discovery truly changed the world and immediately became a useful tool for medical science. Wilhelm Conrad Roentgen

42 Chem 106, Prof. J.T. Spencer 42 Chapt. 2.1 Radioactivity: Wilhelm Roetgen and Henri Becquerel CRT metal target e beam invisibleradiation(X-rays) X-rays - not affected by magnetic fields - passed thru many materials -produced images on film (ionized Ag emulsions) U glowed in dark (phosphorescence) emitted high energy radiation in the dark (radioactivity)

43 Chem 106, Prof. J.T. Spencer Nobel Prize for Radioactivity Pierre and Marie Curie Henri Becquerel

44 Chem 106, Prof. J.T. Spencer 44 The most famous of all women scientists, Marie Sklodowska-Curie is notable for many firsts. In 1903, she became the first woman to win a Nobel Prize for Physics (Pierre Curie and Henri Becquerel, for the discovery of radioactivity. She was also a professor at the Sorbonne University in Paris (1906). In 1911, she won an unprecedented second Nobel Prize (in chemistry for her discovery radium. She was the first person ever to receive two Nobel Prizes.) She was the first mother of a Nobel Prize Laureate; daughter- Nobel Prize Marie Sklodawaska Curie Marie Sklodowska-Curie In 1934, Maria Curie died of leukemia

45 Chem 106, Prof. J.T. Spencer 45 u Marie Curie ( ) - separated the pure radioactive material (Uranium) which was spontaneously radioactive (from the mineral pitchblende)  Ernest Rutheford ( ) - found radiation from uranium was of three types ( , , and  ) Chapt. 2.1 Radioactivity: Marie Curie and Ernest Rutheford slits U - +     - heavy particles with +2 charge, combines with electrons to form helium, 4 He  - electrons with -1 charge  - high energy electromagnetic radiation

46 Chem 106, Prof. J.T. Spencer 46 u Since the electron made up only a small amount of an atom’s mass it was proposed that it must similarly make up a small amount of the atoms volume. Nuclear Atom: Thomson’s Model (ca. 1900) “Plum-pudding” model = electron positive charge spread over sphere

47 Chem 106, Prof. J.T. Spencer 47 Ernest Rutherford ( ) was born on a farm in New Zealand. In 1895 he placed second in a scholarship competition to attend Cambridge University, but was awarded the scholarship when the winner decided to stay home and get married. As a scientist in England, Rutherford did much of the early work on characterizing radioactivity. He also invented the name proton for the nucleus of the hydrogen atom. He received the Nobel Prize in chemistry in Ernest Rutherford

48 Chem 106, Prof. J.T. Spencer 48 Nuclear Atom: Rutheford and the Gold Foil slits  thin gold foil 4 He particles  detector “...as if you fired a 15-inch cannon shell at a piece of tissue paper and it came back and hit you...” found found - most particles passed straight through foil, some had deflections thru small angles BUT some had VERY large deflections (  = 180°) experiment experiment - fired heavy  particles at a thin gold foil and looked for deflections

49 Chem 106, Prof. J.T. Spencer 49 Nuclear Atom: Rutheford and the Gold Foil Gold Foil A A A A C B B  Beam A:C around 13,000:1

50 Chem 106, Prof. J.T. Spencer 50 Based on gold foil experiment and previous work with electrical and nuclear particles, proposed a nuclear theory; (1) atoms are mostly empty space with very dense (pos. charged) nuclear core (< cm dia.) (2) atoms are highly “non-uniform” (3 ) atomic nucleus must contain large electrical forces of considerable mass (since small electron cannot be responsible for such large deflections) Rutheford’s Atom

51 Chem 106, Prof. J.T. Spencer 51 Nature’s Basic Forces u Electromagnetic u Electromagnetic - force between charged or magnetic particles (electrical and magnetic forces are very closely related). DRIVES MOST OF CHEMICAL BEHAVIOR (Coulomb’s Law; F = kQ 1 Q 2 /d 2 ) u Gravitational u Gravitational - force between objects proportional to their masses. u Strong Nuclear u Strong Nuclear - force keeping like charged nucleons (such as protons) together (very strong but very short range). u Weak Nuclear u Weak Nuclear - nuclear force observed in some radioactive behavior (weaker than electromagnetic but stronger than gravitational). +- mm Strong Nucl. > Electromagnetic > Weak Nucl. > Gravitational

52 Chem 106, Prof. J.T. Spencer 52 Modern Atomic Structure u atomic dimensions; nucleus Å and atom Å (1 Å = m) “... if a nucleus were 2 cm (ca. 1 in.) then the atom would be 200 m (ca. 200 yds)” u atom composed of many “subatomic” particles but only three of these are important to chemists u atomic mass (1 amu = 4 x g), charge (1 esc = 1.60 x coul), density (10 14 g/cm 3 ) u atom = dense nucleus with mostly empty space; electrons of most chemical import. (matchbox of nucl. = 2.5 billion tons) particlecharge (esu)mass (amu) proton neutron electron x 10 -4

53 Chem 106, Prof. J.T. Spencer 53 Modern Atomic Structure Sample exercise: The diameter of a carbon atom is 1.5 angstroms. A) express this diameter in picometers

54 Chem 106, Prof. J.T. Spencer 54 Modern Atomic Structure Sample exercise: The diameter of a carbon atom is 1.5 angstroms. A) express this diameter in picometers 1.5 angstroms

55 Chem 106, Prof. J.T. Spencer 55 Modern Atomic Structure Sample exercise: The diameter of a carbon atom is 1.5 angstroms. A) express this diameter in picometers 1.5 angstroms meters 1 angstrom

56 Chem 106, Prof. J.T. Spencer 56 Modern Atomic Structure Sample exercise: The diameter of a carbon atom is 1.5 angstroms. A) express this diameter in picometers 1.5 angstroms meters pm 1 angstrom 1 meter

57 Chem 106, Prof. J.T. Spencer 57 Modern Atomic Structure Sample exercise: The diameter of a carbon atom is 1.5 angstroms. A) express this diameter in picometers 1.5 angstroms meters pm 1 angstrom 1 meter 150 pm

58 Chem 106, Prof. J.T. Spencer 58 Modern Atomic Structure Sample exercise: The diameter of a carbon atom is 1.5 angstroms. B) How many carbon atoms could be aligned side by side in a straight line across the width of a pencil line that is 0.10 mm wide? 0.10 mm 1 meter angstrom 1 carbon 10 3 mm 1 meter 1.5 angs.

59 Chem 106, Prof. J.T. Spencer 59 Modern Atomic Structure Sample exercise: The diameter of a carbon atom is 1.5 angstroms. B) How many carbon atoms could be aligned side by side in a straight line across the width of a pencil line that is 0.10 mm wide? 0.10 mm

60 Chem 106, Prof. J.T. Spencer 60 Modern Atomic Structure Sample exercise: The diameter of a carbon atom is 1.5 angstroms. B) How many carbon atoms could be aligned side by side in a straight line across the width of a pencil line that is 0.10 mm wide? 0.10 mm 1 meter 10 3 mm

61 Chem 106, Prof. J.T. Spencer 61 Modern Atomic Structure Sample exercise: The diameter of a carbon atom is 1.5 angstroms. B) How many carbon atoms could be aligned side by side in a straight line across the width of a pencil line that is 0.10 mm wide? 0.10 mm 1 meter angstrom 10 3 mm 1 meter

62 Chem 106, Prof. J.T. Spencer 62 Modern Atomic Structure Sample exercise: The diameter of a carbon atom is 1.5 angstroms. B) How many carbon atoms could be aligned side by side in a straight line across the width of a pencil line that is 0.10 mm wide? 0.10 mm 1 meter angstrom 1 carbon 10 3 mm 1 meter 1.5 angs.

63 Chem 106, Prof. J.T. Spencer 63 Modern Atomic Structure Sample exercise: The diameter of a carbon atom is 1.5 angstroms. B) How many carbon atoms could be aligned side by side in a straight line across the width of a pencil line that is 0.10 mm wide? 0.10 mm 1 meter angstrom 1 atom 10 3 mm 1 meter 1.5 angs. = 6.7 x 10 5 atoms

64 Chem 106, Prof. J.T. Spencer 64 Atomic Theory: Isotopes u differences/similarities between atoms of an element; u all atoms of an given element have the same number of protons (and therefore the same number of electrons to balance charge) u atoms of an element may have different numbers of neutrons - called isotopes atomic number (Z) - number of protons mass number (A) - number of protons + number of neutrons nuclide - atoms of a specific elemental isotope A E 11 C 12 C 13 C 14 C Z

65 Chem 106, Prof. J.T. Spencer 65 u 7 electrons, 7 protons, 7 neutrons u 8 electrons, 8 protons, 9 neutrons u 17 electrons, 17 protons, 18 neutrons u 92 electrons, 92 protons, 146 neutrons Atomic Theory: Isotopes 14 N 7 17 O 8 35 Cl U 92

66 Chem 106, Prof. J.T. Spencer 66 Sample exercise:How many protons, neutrons, and electrons are in a 39 K atom? Atomic Theory: Isotopes

67 Chem 106, Prof. J.T. Spencer 67 Sample exercise:How many protons, neutrons, and electrons are in a 39 K atom? Atomic# = 19 Atomic Theory: Isotopes

68 Chem 106, Prof. J.T. Spencer 68 Sample exercise:How many protons, neutrons, and electrons are in a 39 K atom? Atomic# = 19# of protons = 19 # of electrons = 19 Atomic Theory: Isotopes

69 Chem 106, Prof. J.T. Spencer 69 Sample exercise:How many protons, neutrons, and electrons are in a 39 K atom? Atomic# = 19# of protons = 19 # of electrons = 19 Mass # = 39 Atomic Theory: Isotopes

70 Chem 106, Prof. J.T. Spencer 70 Sample exercise:How many protons, neutrons, and electrons are in a 39 K atom? Atomic# = 19# of protons = 19 # of electrons = 19 Mass # = = 20 neutrons Atomic Theory: Isotopes

71 Chem 106, Prof. J.T. Spencer 71 Sample exercise:Give the complete chemical symbol for the nuclide that contains 18 protons, 18 electrons, and 22 neutrons. Atomic Theory: Isotopes

72 Chem 106, Prof. J.T. Spencer 72 Sample exercise:Give the complete chemical symbol for the nuclide that contains 18 protons, 18 electrons, and 22 neutrons. Atomic # = 18, element is Argon Atomic Theory: Isotopes

73 Chem 106, Prof. J.T. Spencer 73 Sample exercise:Give the complete chemical symbol for the nuclide that contains 18 protons, 18 electrons, and 22 neutrons. Atomic # = 18, element is Argon 40 Ar Atomic Theory: Isotopes 18

74 Chem 106, Prof. J.T. Spencer 74 Atomic Theory: Isotopes u Allotropes - Different chemical forms of the same element existing in the same physical state. Fullerene Graphite Diamond

75 Chem 106, Prof. J.T. Spencer 75 u Displays chemical reactivity trends and relationships and constructed to account for (and predict) chemical reactivity of the elements. For example: Li, Na, K soft metals, v. reactive w/ water He, Ne, Argases and not reactive F, Cl, Brreactive with many other elements in a similar fashion Cu, Ag, AuMetal w/ similar reactivity Periodic Table; Dmitri Mendeleev (1869)

76 Chem 106, Prof. J.T. Spencer 76 Periodic Table; Dmitri Mendeleev

77 Chem 106, Prof. J.T. Spencer 77 Periodic Table Group or Family Row 1Alkali metalsLi, Na, K,... 2Alkaline earth metalsBe, Mg, Ca,... 16Chalcogens (chalk formers)O, S, Se,... 17Halogens (salt formers)F, Cl, Br,... 18Noble Gases (inert gases)He, Ne, Ar,...

78 Chem 106, Prof. J.T. Spencer 78 Periodic Table alkali metals alkaline earth metals metals metalloids non-metals noble gases rare earth metals metals

79 Chem 106, Prof. J.T. Spencer 79 metalsnon-metals conductorsinsulators shinydull high thermal conductivitythermal insulators solids at RTfreq. non-solids at RT ductilebrittle Periodic Table (1869) Metalloids (along line in table) have properties between metals and non-metals

80 Chem 106, Prof. J.T. Spencer 80 u Molecule - “assembly” of two or more atoms (with properties different from constituent types of atoms (see “Law of Multiple Proportions”). i.e., H 2 O, H 2 O 2, CaCO 3, HNO 3, H 2 SO 4,... u some elements found in nature as molecules (i.e., O 2, N 2, etc... [diatomic]) u Formulas u Molecular - actual numbers and types of atoms in a molecule u Empirical - smallest whole number ratio of constituentStructural - “picture” showing how the atoms are attached to one another Molecules and Ions

81 Chem 106, Prof. J.T. Spencer 81 Molecular Empirical Structural FormulaFormulaFormula H 2 O (water) H 2 O H 2 O 2 (hydr. peroxide) HO C 2 H 4 (ethylene) CH 2 C 6 H 12 O 6 (glucose) CH 2 O Molecules

82 Chem 106, Prof. J.T. Spencer 82 Formulas u Ethylene is a gas at room temperature and is the starting material for for many plastics. Its molecular formula is C 2 H 4 u Ethylene is a gas at room temperature and is the starting material for for many plastics. Its molecular formula is C 2 H 4. –What is its empirical formula? –What other molecular formulas are possible for this same empirical formula?

83 Chem 106, Prof. J.T. Spencer 83 Formulas u Ethylene is a gas at room temperature and is the starting material for for many plastics. Its molecular formula is C 2 H 4 u Ethylene is a gas at room temperature and is the starting material for for many plastics. Its molecular formula is C 2 H 4. –What is its empirical formula? CH 2 –What other molecular formulas are possible for this same empirical formula? C 2 H 4, C 3 H 6, C 4 H 8, C 5 H 10,...

84 Chem 106, Prof. J.T. Spencer 84 Formulas u Cucurbituril is a compound with cage-like molecules big enough to surround and loosely trap smaller molecules. It has the molecular formula C 36 H 36 N 24 O 12 u Cucurbituril is a compound with cage-like molecules big enough to surround and loosely trap smaller molecules. It has the molecular formula C 36 H 36 N 24 O 12. –What is its empirical formula?

85 Chem 106, Prof. J.T. Spencer 85 Formulas u Cucurbituril is a compound with cage-like molecules big enough to surround and loosely trap smaller molecules. It has the molecular formula C 36 H 36 N 24 O 12 u Cucurbituril is a compound with cage-like molecules big enough to surround and loosely trap smaller molecules. It has the molecular formula C 36 H 36 N 24 O 12. –What is its empirical formula? C 3 H 3 N 2 O

86 Chem 106, Prof. J.T. Spencer 86 Formulas Sample exercise: Give the empirical formula for the substance whose molecular formula is Si 2 H 6.

87 Chem 106, Prof. J.T. Spencer 87 Formulas Sample exercise: Give the empirical formula for the substance whose molecular formula is Si 2 H 6. SiH 3

88 Chem 106, Prof. J.T. Spencer 88 u atoms can gain or lose electrons to become charged (called ions) u positive ion = cation negative ion = anion u Na (neutral has 11 electrons) can easily lose 1 electron to become a cation (Na +1 ) Ions

89 Chem 106, Prof. J.T. Spencer 89 u Polyatomic ions; molecules with charges. i.e., NO 3 -1, SO 4 -2, PO 4 -3, etc... u chemical properties of ions may be VERY different from similar neutral species u Predicting charges on ions - use periodic table (gain or lose electrons to end up with the same number as the nearest noble gas) Ions

90 Chem 106, Prof. J.T. Spencer Ions

91 Chem 106, Prof. J.T. Spencer 91 Sample exercise: How many protons and electrons does the Se 2- ion possess? Ions

92 Chem 106, Prof. J.T. Spencer 92 Sample exercise: How many protons and electrons does the Se 2- ion possess? Se atomic number = 34 Ions

93 Chem 106, Prof. J.T. Spencer 93 Sample exercise: How many protons and electrons does the Se 2- ion possess? Se atomic number = 34 # of protons = 34 # of electrons = = 36 Ions

94 Chem 106, Prof. J.T. Spencer 94 u transfer of electrons between atoms, Na + Cl = [Na] + [Cl] - u ionic compounds contain anions and cations, typically combinations of metals and non-metals (molecular compounds, in which electrons are shared, are usually result from the combination of non-metals only); FeS, LiBr, CuSO 4, TiO 4, etc... u total charge is neutral; total (+) = total (-) u ionic compounds are arranged in a 3D array (packing of ping-pong balls) u usually only empirical formulas can be written for ionic compounds (because no real molecular unit in solid phase but “extended” lattice) u usually solids but soluble in water insol. in organic sols. Ionic Compounds

95 Chem 106, Prof. J.T. Spencer 95 Cation Anion ChargesEmpirical Formula sodium (Na)chlorine (Cl)Na +1 + Cl -1 NaCl magnesium(Mg)nitrogen (N)Mg +2 + N -3 Mg 3 N 2 aluminum (Al)bromine (Br)Al +3 + Br -1 AlBr 3 barium (Ba)sulfate (SO 4 )Ba +2 + SO 4 -2 BaSO 4 lithium (Li)carbonate (CO 3 )Li +1 + CO 3 -2 Li 2 CO 3 nickel (Ni)chloride (Cl)Ni +2 + Cl -1 NiCl 2 Ni +3 + Cl -1 NiCl 3 u total charge is neutral; total (+) = total (-) Ionic Compounds

96 Chem 106, Prof. J.T. Spencer Ionic Compounds Unit Cell Cell Face

97 Chem 106, Prof. J.T. Spencer 97 Sample exercise: Which of the following compounds are molecular? CI 4 FeS P4O6P4O6 PbF 2 Ionic Compounds

98 Chem 106, Prof. J.T. Spencer 98 Sample exercise: Which of the following compounds are molecular? CI 4 FeS P4O6P4O6 PbF 2 Ionic Compounds

99 Chem 106, Prof. J.T. Spencer 99 Sample exercise: Write the empirical formulas for the compounds formed by the following ions: a) Na + and PO 4 3- Ionic Compounds

100 Chem 106, Prof. J.T. Spencer 100 Sample exercise: Write the empirical formulas for the compounds formed by the following ions: a) Na + and PO 4 3- Na 3 PO 4 Ionic Compounds

101 Chem 106, Prof. J.T. Spencer 101 Sample exercise: Write the empirical formulas for the compounds formed by the following ions: b) Zn 2+ and SO 4 2- Ionic Compounds

102 Chem 106, Prof. J.T. Spencer 102 Sample exercise: Write the empirical formulas for the compounds formed by the following ions: b) Zn 2+ and SO 4 2- ZnSO 4 Ionic Compounds

103 Chem 106, Prof. J.T. Spencer 103 Sample exercise: Write the empirical formulas for the compounds formed by the following ions: c) Fe 3+ and CO 3 2- Ionic Compounds

104 Chem 106, Prof. J.T. Spencer 104 Sample exercise: Write the empirical formulas for the compounds formed by the following ions: c) Fe 3+ and CO 3 2- Fe 2 (CO 3 ) 3 Ionic Compounds

105 Chem 106, Prof. J.T. Spencer 105 u Method for unambiguously referring to the a. 15 million known molecules) u Organic compounds - containing C combined typically with H, O, N, and S (originally associated with living organisms but no longer relevant definition) u Inorganic compounds - all other compounds Nomenclature: naming inorganic compounds

106 Chem 106, Prof. J.T. Spencer 106 u Traditional names for compounds long known (ammonia [NH 3 ], water [H 2 O], Zeise’s salt [Pt(C 2 H 4 )Cl 3 ] -1 ], Muriatic Acid [HCl], etc...) u common names (somewhat systematic, ferrous chloride, cupric chloride, etc...) u International Union of Pure and Applied Chemistry rules (IUPAC) Nomenclature: naming inorganic compounds

107 Chem 106, Prof. J.T. Spencer 107 u Ionic compounds are names based upon the component ions. u Positive ion (cation) named and written first u Negative ion (anion) named and written last u Solve ambiguity in charge by using Roman numerals Nomenclature: naming ionic compounds CationAnion Compound Name Na + ClNaClsodium chloride Na + Cl - NaClsodium chloride Al +3 O -2 Al 2 O 3 aluminum oxide Fe +2 O -2 FeOiron(II) oxide (ferrous oxide) (ferrous oxide) Fe +3 O -2 Fe 2 O 3 iron(III) oxide (ferric oxide) (ferric oxide)

108 Chem 106, Prof. J.T. Spencer 108 u Monoatomic - take the name from the element »Li +1 lithium ionSr +3 strontium ion »Ca +2 calcium ion u Polyatomic - only one common polyatomic cation »NH 4 +1 ammonium ion u Multiple Cationic Charge Possible - specify charge with Roman numerals to be unambiguous »Fe +2 iron(II) ionFe +3 iron(III) ion »Cr +6 chromium(VI) ionCr +5 chromium(V) ion u For metals, older method used to distinguish between ions differing by one charge unit by adding suffix (-ous for lower charge, -ic for higher charge) »Fe +2 ferrous ionFe +3 ferric ion »Co +2 cobaltous ionCo +3 cobaltic ion Nomenclature: naming cations

109 Chem 106, Prof. J.T. Spencer 109 Nomenclature: naming anions u Monoatomic - add -ide suffix »F -1 fluoride ionP -3 phosphide ion »O -2 oxide ionB -5 boride ion u Polyatomic - some common use -ide suffix »OH -1 hydroxide ionCN -1 cyanide ion »N 3 -1 azide ionO 2-2 peroxide ion u Oxyanions - (1) when only two, the one with less oxygen ends in -ite and the one with more oxygen ends with -ate »NO 2 -1 nitrite ionNO 3 -1 nitrate ion »SO 3 -2 sulfite ionSO 4 -2 sulfate ion u Oxyanions- for species with more than two members use prefixes (hypo- less oxygen and per- more oxygen) ClO -1 ClO 2 -1 ClO 3 -1 ClO 4 -1 hypochlorite chlorite chlorate perchlorate

110 Chem 106, Prof. J.T. Spencer 110 u Acid - compound which yields H + when dissolved in water u write hydrogen first; HCl, H 2 SO 4, H 3 PO 4, etc... u anions which end in -ide use hydro- as prefix and -ic as suffix Nomenclature: acids AnionAcid Cl - (chloride)HCl (hydrochloric acid) F - (fluoride)HF (hydrofluoric acid) u oxyacids - replace -ate suffix of anion with -ic, replace -ite suffix of anion with -ous (leave prefixes!) AnionAcid ClO 2 - (chlorite)HClO 2 (chlorous acid) ClO 3 - (chlorate)HClO 3 (chloric acid) ClO 4 -1 (perchloric)HClO 4 (perchloric acid)

111 Chem 106, Prof. J.T. Spencer 111 u Similar to ionic compounds –More positive element (left and down on periodic table) named first (first in formula also) –Second element name ends with -ide –Use numbering prefixes if necessary Nomenclature: molecular compounds Prefix Number Mono-1 Di-2 Tri-3 Tetra-4 Penta-5 Hexa-6 Hepta-7 Octa-8 Nona-9 Deca-10 FormulaName FormulaName (text prob. 2.45) N 2 O 5 dinitrogen pentoxide IF 7 iodine heptafluoride XeO 3 xeon trioxide SiCl 4 silicon tetrachloride H 2 Sedihydrogen selenide P 4 O 6 tetraphosphorus hexoxide

112 Chem 106, Prof. J.T. Spencer 112 u zinc(II) chloride u ammonium sulfate u iron(III) fluoride u hydrobromic acid u perbromic acid u sulfur hexafluoride u hydrogen cyanide Nomenclature: examples FormulaName ZnCl 2 (NH 4 ) 2 SO 4 FeF 3 HBr HBrO 4 SF 6 HCN

113 Chem 106, Prof. J.T. Spencer 113 u Atomic Theory u Experiments leading to the discovery of atomic structure u The Periodic Table u Molecules and Ions u Nomenclature End Chapter 2


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