Chapter 3 pages Modern Chemistry Chapter 3 Atoms: the building block of matter
Chapter 3 pages Section 1 Atoms: From Philosophical Idea to Scientific Theory
Chapter 3 pages Foundation of Chemical Atomic Theory Law of Conservation of Mass –Mass is neither created or destroyed during ordinary chemical reactions or physical changes
Chapter 3 pages Law of Conservation of Mass Image p. 69*
Chapter 3 pages Law of Conservation of Mass Image p. 69*
Chapter 3 pages Foundation of Chemical Atomic Theory Law of Definite Proportions –A chemical compound contains the same elements in exactly the same proportions by mass regardless of the size of the sample or the source of the compound.
Chapter 3 pages Foundation of Chemical Atomic Theory Law of Multiple Proportions –If two or more different compounds are composed of the same two elements then the ratio of the masses of the second element combined with a certain mass of the first element is always a ratio of small whole numbers.
Chapter 3 pages Law of Multiple Proportions Image p. 69*
Chapter 3 pages Dalton’s Atomic Theory 1. All matter is composed of extremely small particles called atoms
Chapter 3 pages Dalton’s Atomic Theory 2. Atoms of a given element are identical in size, mass and other properties; atoms of different elements differ in size, mass and other properties.
Chapter 3 pages Dalton’s Atomic Theory 3. Atoms cannot be subdivided, created or destroyed.
Chapter 3 pages Dalton’s Atomic Theory 4. Atoms of different elements combine in simple whole-number ratios to form chemical compounds.
Chapter 3 pages Dalton’s Atomic Theory 5. In chemical reactions, atoms are combined, separated or rearranged.
Chapter 3 pages Modern Atomic Theory Leucippus Democritus Atomic Theory Tested by experiment and modified with new discoveries and experiments
Chapter 3 pages Section 2 The Structure of the Atom
Chapter 3 pages Discovery of the Electron Cathode Ray Tube Experiment - Thompson Observations –Cathode Rays are deflected a magnetic field. –Cathode rays are deflected from a negatively charged object. –Charge to mass ratio is always the same for the cathode rays.
Chapter 3 pages Discovery of the Electron Cathode Ray Tube Experiment - Thompson Conclusion –Cathode rays are composed of negatively charged particles –Named “electrons”
Chapter 3 pages Discovery of the Electron Oil Drop Experiment - Millikan –Measured the charge of the electron –Calculated the mass of an electron x kg
Chapter 3 pages Discovery of the Electron Inferences –Atoms are neutral, so there must be a positive charge. –Electrons are small, so there must be other particles.
Chapter 3 pages Discovery of the Electron Plum Pudding Model –Negative electrons were spread evenly throughout the positive charge.
Chapter 3 pages Discovery of the Electron
Chapter 3 pages Discovery of the Atomic Nucleus Gold Foil Experiment – Rutherford et. al –Hypothesis: Alpha particles would pass through with slight deflection. –Observation: 1 in 8000 particles were deflected back to the source. –Conclusion: The atom contains a small densely packed bundle of matter with a positive charge –Named the “nucleus”
Chapter 3 pages Gold Foil Animation Insert Glencoe Disk 1 and click on picture for animation.
Chapter 3 pages Gold Foil Animation
Chapter 3 pages Gold Foil Experiment Image p. 75
Chapter 3 pages Discovery of the Atomic Nucleus Relative size of the nucleus
Chapter 3 pages Composition of The Atomic Nucleus Nuclei contain protons and neutrons Neutral because number of protons equal number of electrons Each element has a different number of protons in their nucleus –The number of protons determines the atom’s identity Nuclear forces hold protons & neutrons together
Chapter 3 pages Properties of Subatomic Particles p. 76
Chapter 3 pages While the number of protons in the nucleus defines an element's identity, variations on the number of neutrons in the nucleus give rise to different isotopes of the same element. Isotopes of hydrogen
Chapter 3 pages Gold Foil Experiment Photo
Chapter 3 pages Gold Foil Experiment Photo
Chapter 3 pages Thompson and Rutherford Photo
Chapter 3 pages Section 2 Homework Ch 3 Sec 2 Review Page 76 #1-5
Chapter 3 pages Section 3 Counting Atoms
Chapter 3 pages Atomic Number The number of protons of each atom of that element Identifies the element
Chapter 3 pages Isotopes Atoms of the same element that have different masses equals the isotope Isotopes do not differ significantly in their chemical behavior
Chapter 3 pages Mass Numbers Mass numbers = # of p + + # of n 0 of a specific isotope
Chapter 3 pages Designating Isotopes Hyphen notation –name of element – mass number –Hydrogen – 3 Nuclear symbol mass number atomic number
Chapter 3 pages Number of neutrons in an atom neutrons = mass number – atomic number (This is how to calculate isotopes…) Nuclide – a general term for a specific isotope of an element **Practice Problems page 87 #2-3
Chapter 3 pages Relative Atomic Mass One atom, carbon-12, is set as a standard All masses are expressed in relation to this standard 1 atomic mass unit = 1/12 the mass of a carbon-12 atom
Chapter 3 pages Relative Atomic Mass Examples –Hydrogen – 1 = amu –Oxygen – 16 = amu –Magnesium – 24 = amu p + = amu, n 0 = amu, e - = amu Relative mass and mass number are close in value but not the same
Chapter 3 pages Average Atomic Mass The weighted average of the atomic masses of the naturally occurring isotopes of an element Example –Copper Cu-63:.6915 x amu = Cu-65:.3085 x amu = amu percent relative mass
Chapter 3 pages The Mole An amount of a substance that contains as many particles as there are atoms in exactly 12 g carbon-12. Similar to a dozen or a pair or a gross x carbon-12 atoms = 12 grams of carbon-12 Avogadro’s number = x particles
Chapter 3 pages Molar mass The mass of one mole of a pure substance Unit = g/mol On the periodic table, use 4 sig. figs.
Chapter 3 pages Gram-Mole Conversions The conversion factor for gram-mole conversion is molar mass. What is the mass, in grams, of 3.50 moles of Cu? –222 grams Cu OR g mol g
Chapter 3 pages Practice Problems page 85 1.What is the mass in grams of 2.25 mol of the element iron? 2.What is the mass in grams of mol of the element potassium? 3.What is the mass in grams of mol of the element sodium? 4.What is the mass in grams of 16.3 mol of the element nickel? p g Fe 14.7 g K g Na 957 g Ni
Chapter 3 pages Conversions Image p. 84
Chapter 3 pages Gram-Mole Conversions The conversion factor for gram-mole conversion is molar mass. A Chemist produced 11.9 g of Al. How many moles of Al were produced? –0.411 moles Al OR g mol g
Chapter 3 pages Practice Problems page 85 1.How many moles of calcium are in 5.00 g of calcium? 2.How many moles of gold are in 3.60 x g of gold? 3.How many moles of zinc are in g of zinc? p mol Ca 1.83 x mol Au 8.18 x mol Zn
Chapter 3 pages Conversions with Avogadro’s Number The conversion factor for particle-mole conversion is Avogadro’s number. How many moles of silver are in 3.01 x atoms of silver –0.500 moles Ag OR 6.022x10 23 atoms 1 mol 6.022x10 23 atoms 1 mol
Chapter 3 pages Practice Problems page 86 1.How many moles of lead are 1.50 x atoms of lead? 2.How many moles of tin are in 2500 atoms of tin? 3.How many atoms of aluminum are in 2.75 mol of aluminum? p. xx 2.49 x mol Pb 4.2 x mol Sn 1.66 x atoms Al
Chapter 3 pages Conversions with Avogadro’s Number The conversion factor for particle-mole conversion is Avogadro’s number. What is the mass, in grams, of 1.20x10 18 atoms of Cu? –1.27 x g Cu OR 6.022x10 23 atoms 1 mol 6.022x10 23 atoms 1 mol
Chapter 3 pages Practice Problems page 87 1.What is the mass in grams of 7.5 x atoms of nickel? 2.How many atoms of sulfur are in 4.00 g of sulfur? 3.What mass of gold contains the same number of atoms as 9.0 g of aluminum? p. xx 7.3 x g Ni 7.51 x atoms S 66 g Au
Chapter 3 pages Conversions Image p. 84
Chapter 3 pages Section 1 Homework Section Review Page 87 #1-7