2 Pudding and Clouds Chem Catalyst: In the 5th century a Greek philosopher named Leucippus and his student, Democritus, said, “ All matter is made up of particles called atoms.”Do you think atoms are composed of smaller pieces?If there are smaller pieces of an atom , how would they differ from each other?
3 Connections to the past On the cards used in “Create a Table”:What do you think the size of the circle represents?What do you think the pegs or sticks represent?
4 AtomsAtoms are extremely small particles, which cannot be seen with the eye or regular school microscopesAn atom is the smallest amount of a element that can exist and still have the properties of that elementAll matter is made up of atoms.
5 Charge Fundamental property of atom and their parts Related to the forces pushing or pulling the atom piecesA piece can have positive, negative or neutral charge
6 For most of timePeople were talking about atoms without having ever actually seen any picture of one.They came up with visual and descriptive representations of concept of an atom, called a model or theory
7 Atomic modelAtomic model or theory represent the best explanation for the design and workings of an atom by a specific person or group, based on the scientific evidence availableAs new evidence is gathered, models are refined and changed.
8 Theories and models are not casual ideas Not proposed without testing, and researchThen it is tested repeatedly by the scientific communityIt is valid until contrary evidence is found, then modified or discarded.
9 The Big QuestionHow have chemists thought about the atom through history?Unit 1 • Investigation III
10 Goal of the sectionBy the completion of the section you should be able to:Identify the major components of any atomUse the concepts of the latest theory on atomic structure to explain how a atom is set up and operatesUnderstand the 5 major versions of atomic theory and be able to compare and contrast them
11 ActivityPurpose: This lesson will introduce you to various models for the atom that have appeared over the past two hundred years. The descriptions of five models of the atom are on a separate handout.(cont.)Unit 1 • Investigation III
12 Part 1 Organize the models in chronological order Based on information listed on the cards, organize the models in chronological order.In comp book List models A thru E from earliest model to current model. Explain what evidence you used to arrange models
13 Part 2: Organizing Models and evidence by Year and Name A 2nd set of handouts will be given to students.Use 2nd handout set to determine if your original chronological order of models was correct.In Comp book, create and complete a chart with the following information
14 DoesModelIndicateExistenceof:Model NamePeople behind model conceptElectronProtonNeutronsNucleusElectrons moving in paths or orbitsElectrons moving randomlyBilliardBallPlumPuddingNuclearSolarSystemCurrent
15 Part 3: Matching evidence with Models Each pair of students will then be given 6 pieces of evidence about atoms.For each piece of evidence, compare the information of 2 models to determine which model supports or agrees with the piece of evidence the best. Explain your answer in your composition book
16 (cont.)Five Models of the AtomUnit 1 • Investigation III
17 Five authors and their big ideas John Dalton Atom as a solid sphere, Different atom for each elementJJ Thompson ElectronsErnest Rutherford NucleusNiels Bohr Electron Orbitals/ShellsProtonsHeisenberg,Chadwick Electron Cloud / Neutron
19 Alpha particlesHelium nucleus stripped of its electrons
20 Current ModelEvery atom is composed of a tiny, dense, positively charged nucleus located at center of atom. Nucleus is composed of positively charges protons and neutrally charged neutronsMass of a proton and neutron are the sameElectron Cloud: region of atom around the nucleus occupied by fast moving, almost mass-less, negatively charged electrons.An atom (and electron cloud) is made up mostly of space, almost all mass of atom is located in the nucleusElectrons do not all move at the same distance from the nucleus. Some are closer or farther away ,depending on amount of KE they possessPaths of electrons are not orbits like planets, but more randomized. It is impossible to predict the exact location of an electron at a point of time.
22 Part 4 In comp book, write Definitions for: Proton Neutron Electron NucleusElectron Cloud, orbit, shellVoid
23 Difference between clouds, orbits and shells Electron cloud: Includes all space in an atom outside of a nucleus where an electron may be found, mostly voidElectron Orbit: 2 Dimension representation of an electron’s position based on the amount of KE energy it possessesElectron Shell: 3 dimensional representation of a electron orbit
25 Wrap-UpAll matter is made up of extremely small particles called atoms. These particles are too small to be seen even with a regular microscope.Science is theoretical and dynamic. Models and theories are continually being revised, refined, or replaced with new models and theories.Unit 1 • Investigation III
26 Check in Does a nucleus have a positive, negative or neutral charge Which has more mass?A proton from a Helium atomAn electron from a Helium atomA neutron from a Helium atomA nucleus from a helium atomAn alpha particle
27 Check in#3 Match the Scientist’s name to the Model Name below to which he is associated. Organize from oldest (1) to most recent (5)Chadwick Plum PuddingBohr Solar SystemDalton Current ModelThomson Billiard BallHeisenberg NucleusRutherford