Topic 2.1: Atomic Structure Honors Chemistry 2014-15 Mrs. Peters 1.
HISTORY OF THE ATOMIC MODEL ATOMIC THEORY Mrs. Gibson Physical Science.
-
Upload
darcy-grant -
Category
Documents
-
view
265 -
download
1
Transcript of HISTORY OF THE ATOMIC MODEL ATOMIC THEORY Mrs. Gibson Physical Science.
HISTORYHISTORY OFOF THE ATOMIC MODELTHE ATOMIC MODEL
ATOMIC THEORYATOMIC THEORY
Mrs. Gibson
Physical Science
Democritus 400BCDemocritus 400BC
Proposed all objects have a smallest Proposed all objects have a smallest part/piecepart/piece
Named this smallest piece – Named this smallest piece – atomatom Atomos means indivisible, not to be cutAtomos means indivisible, not to be cut Atom – small hard particle, made of Atom – small hard particle, made of
same material, but in different sizes, same material, but in different sizes, shapes, and colors, indefinite in shapes, and colors, indefinite in number, always moving, join together.number, always moving, join together.
Uses observations to prove ideasUses observations to prove ideas
DALTON’SFour Points on the
Atomic Theory
All matter is All matter is made of atoms. made of atoms.
Atoms are Atoms are indivisible indivisible
and and indestructibleindestructible..
Atomsof 2 or morekinds make
up acompound
Atomsrearrangeduring a chemicalreaction
Atoms with thesame mass and
propertiesmake up an
element
John Dalton 1803John Dalton 1803
Uses scientific reasoning to prove ideasUses scientific reasoning to prove ideas
J. J. Thomson 1897J. J. Thomson 1897 Discovers that the atom is Discovers that the atom is divisibledivisible.. Theory is called Theory is called Plum Pudding ModelPlum Pudding Model
Atom is positive material with negative Atom is positive material with negative particles mixed in.particles mixed in.
Discovers Discovers ElectronElectron called it a corpuscle called it a corpuscle Discovers electron by passing electric current Discovers electron by passing electric current
through a gasthrough a gas Gas is neutral, but gives off negative charges.Gas is neutral, but gives off negative charges. Reasoned: If there is a negative charge, then Reasoned: If there is a negative charge, then
there must be a positive substance to make there must be a positive substance to make the gas neutralthe gas neutral..
Ernest Rutherford 1908Ernest Rutherford 1908
Gold Foil ExperimentGold Foil ExperimentDiscovers center of atom, Discovers center of atom,
Nucleus,Nucleus, contains positive contains positive ProtonsProtons
Atom has positive center Atom has positive center with negative charges with negative charges (electrons) scattered outside (electrons) scattered outside in in electron cloud.electron cloud.
Most of atom is empty spaceMost of atom is empty space
GOLD FOIL EXPERIMENTGOLD FOIL EXPERIMENT
Gold atoms and alpha
particles (path) up close
Most of the particles pass through the gold foil-some particles bounce back- must be a “solid” middle and it must be positive since it repels the other alpha particles-negative particles must be floating in the empty space
Two atoms were walking down the street Two atoms were walking down the street when one stops and shoutswhen one stops and shouts
“ “Wait! Stop! I lost an electron.”Wait! Stop! I lost an electron.”
““You did? Are you sure?” says the second You did? Are you sure?” says the second atom frantically.atom frantically.
““Yes,” says the first “I’m POSITIVE!”Yes,” says the first “I’m POSITIVE!”
Wait for it...
Laughter and Applause
Niels Bohr 1913Niels Bohr 1913Changed Rutherford’s model Changed Rutherford’s model
Show that electrons are not Show that electrons are not just scattered, but travel just scattered, but travel around nucleus in around nucleus in orbitalsorbitals called called energy levelsenergy levels..
The Bohr Model is used most The Bohr Model is used most to represent atomic structureto represent atomic structure
Chadwick Finds Neutron by…Chadwick Finds Neutron by…
Chadwick concluded that the energy of the protons could be explained by the presence of a neutral particle comparable in mass to that of a proton.
Wave ModelWave Model Current Model Theory, based on wave Current Model Theory, based on wave
mechanicsmechanicsCannot determine exact location of Cannot determine exact location of
electrons, but can determine probable electrons, but can determine probable locations based on calculations.locations based on calculations.
Energy Levels fillEnergy Levels fill2 - 1st2 - 1st8- 2nd8- 2nd8-18 in 3rd 8-18 in 3rd
Let’s Explore Electron Let’s Explore Electron Configuration…Configuration…
Electron AppletElectron Applet
http://www.colorado.edu/physics/2000/applets/a3.htmlhttp://www.colorado.edu/physics/2000/applets/a3.html
For more information try the tutorial: For more information try the tutorial: Elements as AtomsElements as Atoms
http://www.colorado.edu/physics/2000/elements_as_atoms/index.htmlhttp://www.colorado.edu/physics/2000/elements_as_atoms/index.html
SummarySummary
What was the What was the Theory of…Theory of… Democritus?Democritus? Dalton?Dalton? Thomson?Thomson? Rutherford?Rutherford? Bohr?Bohr? Chadwick?Chadwick? Wave?Wave?
Who discovered the…Who discovered the… Electron?Electron? Proton?Proton? Nucleus?Nucleus? Neutron?Neutron?
What allows the What allows the scientists to scientists to develop/discover each develop/discover each new piece of the new piece of the atomic model?atomic model?