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Historical Atomic ModelsHistorical Atomic Models
ABC II BABC II B
Ms. PollockMs. Pollock
Spring 2007Spring 2007
DemocritusDemocritus
Democritus’s Theory of Democritus’s Theory of Atomic StructureAtomic Structure
First to propose atomic theoryFirst to propose atomic theory 400 BCE400 BCE Atoms “atomos” are indivisible.Atoms “atomos” are indivisible. Leads to Aristotle’s belief that Leads to Aristotle’s belief that
matter is made of 4 elements – matter is made of 4 elements – earth, air, water, and fireearth, air, water, and fire
John DaltonJohn Dalton
Dalton’s Atomic TheoryDalton’s Atomic Theory
1806 published 1806 published theorytheory
English teacher and English teacher and climatologistclimatologist
QuakerQuaker Discovered color Discovered color
blindnessblindness Very careful, Very careful,
repeatable repeatable measurementsmeasurements
Dalton’s Atomic TheoryDalton’s Atomic Theory
Elements made of tiny particles, called Elements made of tiny particles, called atomsatoms
All atoms of given element identicalAll atoms of given element identical Elements of different atoms different Elements of different atoms different
from each otherfrom each other Atoms combined to make compoundsAtoms combined to make compounds Atoms not able to be created or Atoms not able to be created or
divided; only recombined in a reactiondivided; only recombined in a reaction
William CrookesWilliam Crookes
Crookes’ TubeCrookes’ Tube
Developed cathode-ray tubesDeveloped cathode-ray tubes– Control of electron beamControl of electron beam– Discovery of new particles inside Discovery of new particles inside
atomsatoms Device used in televisionsDevice used in televisions Discovery of thallium and heliumDiscovery of thallium and helium
Crookes TubeCrookes Tube
J. J. ThomsonJ. J. Thomson
Thomson and the AtomThomson and the Atom
Plum Pudding Plum Pudding ModelModel
Discovered Discovered electron in 1897electron in 1897
Found cathode Found cathode rays would bend rays would bend toward positive toward positive charge, so must charge, so must be negativebe negative
Ernest RutherfordErnest Rutherford
Rutherford’s ContributionRutherford’s Contribution
Discovered large Discovered large positive charge in positive charge in center of atomcenter of atom
Gold foil Gold foil experimentexperiment
Discovered protonDiscovered proton 19091909
Niels BohrNiels Bohr
Bohr ModelsBohr Models
Electrons orbiting Electrons orbiting nucleus in special nucleus in special orbitsorbits
Nucleus very smallNucleus very small 19131913 Electrons only Electrons only
found in certain found in certain places in the atomplaces in the atom
Albert EinsteinAlbert Einstein
EinsteinEinstein
Much energy released from small Much energy released from small amounts of matteramounts of matter
E = mcE = mc22
Aided in development of atomic Aided in development of atomic bombbomb
Connection of many physics Connection of many physics theories and beliefs through one theories and beliefs through one formulaformula
Max PlanckMax Planck
PlanckPlanck
Father of quantum mechanicsFather of quantum mechanics Energy not continuous, released in Energy not continuous, released in
quantaquanta Developed universal constant of Developed universal constant of
energyenergy Calculated energy based on Calculated energy based on
electromagnetic frequency and electromagnetic frequency and constantconstant