![Calculating Atomic massAtomic mass = [(relative abundance)(atomic mass of the isotope)] for each naturally occurring isotopeMultiply the relative abundances (expressed as a decimal) times the mass of each isotope then add the results](https://image.slidesharecdn.com/atomicstructure-110830105323-phpapp01/85/Atomic-structure-34-320.jpg)
Atomic structure
- 1. Atomic StructureDefining the Atom
- 2. OpeningWhat are we going to learn today?Essential Questions: How did Democritus describe atoms?How did John Dalton further Democritus’s ideas on atoms?What instruments are used to observe individual atoms?GPS Standards:SCSh1b – Recognize that different explanations can be given for the same informationSCSh7c – Understand how major shifts in scientific knowledge occur.SCSh7d – Hypotheses often cause scientists to develop new experiments that produce additional data.SCSh7e – Testing, revising and occasionally rejecting new and old theories never ends.
- 3. Why are we doing this? (logbook)What are some objects that require experimental data in order to “picture” them, either because they are small or inaccessible?Here’s how. (agenda)Discuss early models of the atomBegin gathering information for an atomic theory timeline.Complete Section Review WSWrap-upEvaluate and criticize the following statements:“All atoms are identical.”Chemical reactions occur when atoms of one element change into atoms of another element.”
- 4. Early Models of the atomatomSmallest particle of an element that retains its identity in a chemical reactionDemocritus (460BC – 370BC)Greek philosopherOne of the first to suggest the existence of atomsBelieved that atoms were indivisible and indestructibleNo attempt to explain chemical behaviorNo experimental support
- 5. John Dalton (1766 – 1844)English chemist and schoolteacherDalton’s atomic theoryAll elements are composed of tiny indivisible particles called atoms.Atoms of the same element are identical. The atoms of any one element are different from those of any other element.Atoms of different elements can physically mix together or can chemically combine in simple whole-number ratios to form compounds.Chemical reactions occur when atoms are separated, joined, or rearranged. Atoms of one element, however, are never changed into atoms of another element as a result of a chemical reaction.
- 6. Sizing up atomsPure copper penny contains about 2.4x1022 atoms of copper6x109 people on EarthRadius of most atoms is between 5x10-11m and 2x10-10m.Individual atoms can only be observed by scanning tunneling electron microscope
- 7. Scanning tunneling electron microscope
- 8. SCE Microscope depiction of electron cloud
- 9. Diagram of scanning tunneling electron microscope
- 10. Quantum forest
- 11. Opening – 8/29/11What are we going to learn today?GPS StandardsSCSh1b – Recognize that different explanations can be given for the same informationSCSh1c – Explain that further understanding of scientific problems relies on the design and execution of new experiments which may reinforce or weaken opposing explanations.SCSh7c – Understand how major shifts in scientific knowledge occur.SCSh7d – Hypotheses often cause scientists to develop new experiments that produce additional data.SCSh7e – Testing, revising and occasionally rejecting new and old theories never ends.SC3a – Discriminate between the relative size, charge, and position of protons, neutrons, and electrons in the atom.
- 12. Why are we doing this? Essential Questions What are 3 kinds of subatomic particles?How can you describe the structure of the nuclear atom?Here’s how. (agenda)Notes/discussion about the discovery of protons, neutrons, and electronsStudents work in pairs to complete a chart about the three subatomic particles.Complete Section 4.2 Review Sheet
- 13. Subatomic particlesThree kinds of subatomic particlesProtonPositive chargeNeutronNo chargeElectronNegative charge
- 14. Discovery of the electronJ.J. Thomson (1856 – 1940)Discovered the electron in 1897Cathode ray tube experimentsHypothesized that cathode rays are tiny negatively charged particles moving at high speed (electrons)Measured the charge to mass ratio of the electronPlum Pudding Model
- 15. Cathode ray deflected by a magnetPlum Pudding Model
- 16. Robert Millikan (1868 – 1953)determined the quantity of charge on an electronUsed Thomson’s charge-mass ratio to calculate the mass of the electron (1916)Oil drop experiments
- 17. Millikan oil drop experiment
- 18. Discovery of the protonEugen Goldstein (1850 – 1930)Found rays traveling in the direction opposite to that of the cathode rays in a cathode ray tubeCalled these rays canal rays (later renamed protons)
- 19. Discovery of the NeutronJames Chadwick (1891 – 1974)Discovered the neutron (1932)
- 20. Properties of subatomic particles
- 21. Discovery of the NucleusErnest Rutherford (1871 – 1937)Gold foil experiments (1911)FindingsAtom is mostly empty spaceSmall positively charged nucleusElectrons move around outside the nucleusNuclear model
- 22. Explanation of results of gold foil experiment
- 23. Comparison of Thomson’s plum pudding model (top) and Rutherford’s nuclear model (bottom) Notice that the nucleus in this model is solid. Protons and neutrons had not been discovered.
- 24. Ticket out the doorWrite a paragraph explaining how Rutherford’s gold foil experiment yielded new evidence about atomic structure. Hint: First describe the setup of the experiment. The explain how Rutherford interpreted his experimental data.
- 25. OpeningEssential Questions: What makes one element different from another?How do you find the number of neutrons in an atom?How do isotopes of an element differ?How do you calculate the atomic mass of an element?Why is the periodic table useful?GPS Standards:SC3c – Explain the relationship of the proton number to the element’s identity.SC3d – Explain the relationship of isotopes to the relative abundance of atoms of a particular element.
- 26. Atomic NumberThe number of protons in an atom identifies the element.Atomic numberthe number of protons in the nucleus of an atomEach element has a unique atomic numberBecause atoms are neutral, the number of electrons(-1) must equal the number of protons(+1).
- 27. Sample Problem p. 111How many protons and electron are in each of the following atoms?FluorineCalciumAluminum
- 28. Mass NumberMass number Total number of protons and neutrons in the nucleus of the atom# neutrons = mass number – atomic number
- 29. Hyphen notationName of element followed by a hyphen and the mass numberExamples Carbon – 12Carbon – 14Oxygen – 18
- 30. Nuclear NotationThe symbol of the elementMass number as a superscript before the symbolAtomic number as a subscript before the symbol
- 31. isotopesIsotopes atoms of the same element that have different massesAtoms that have the same number of protons but different numbers of neutronsAtoms that have the same atomic number but different mass numbers
- 32. Isotopes of hydrogenProtiumHydrogen – 1DeuteriumHydrogen – 2TritiumHydrogen – 3
- 33. Atomic massAtomic mass unit (amu)1/12 the mass of a carbon-12 atomMass of a single proton or neutron is approximately 1amuAtomic mass weighted average mass (in amu) of the atoms in a naturally occurring sample of an elementMass shown on the periodic table
- 34. Calculating Atomic massAtomic mass = [(relative abundance)(atomic mass of the isotope)] for each naturally occurring isotopeMultiply the relative abundances (expressed as a decimal) times the mass of each isotope then add the results
- 35. Sample problem, p. 117Atomic mass = 1.993 amu + 8.817 amu = 10.81 amu
- 36. Periodic Table PreviewPeriodic table – an arrangement of elements in which the elements are separated into groups based on a set of repeating propertiesPeriod Horizontal row on the Periodic Table7 periodsProperties vary as you move across a periodGroup or familyVertical column of the Periodic Table18 groupsElements within a group have similar properties