Post on 14-Dec-2015
Atomic Models:Atomic Models:From Hypothesis to From Hypothesis to
TheoryTheory
http://www.youtube.com/watch?v=bw5TE5o7JtE&feature=BFa&list=PLE2B5C43C0BC88688&lf=results_main
The Greek ModelThe Greek Model440 BC: Leucippus & 440 BC: Leucippus &
Democritus hypothesize Democritus hypothesize that matter is made of that matter is made of atoms atoms
Explained why different Explained why different substances have different substances have different propertiesproperties
Performed no Performed no experimentsexperiments
Very little evidence to Very little evidence to support hypothesissupport hypothesis
Democritus of Abdera
The Greek ModelThe Greek Model Five major pointsFive major points
1.1. All matter is composed of atomsAll matter is composed of atoms too small to be seentoo small to be seen CANNOT be split into smaller partsCANNOT be split into smaller parts
2.2. There is a void, which is empty space between There is a void, which is empty space between atomsatoms
3.3. Atoms are completely solidAtoms are completely solid
4.4. Atoms are homogeneous, with no internal structureAtoms are homogeneous, with no internal structure
5.5. Atoms are different in size, shape, and weightAtoms are different in size, shape, and weight
The Dalton ModelThe Dalton Model
1803: John Dalton (England) 1803: John Dalton (England) re-introduced the atomic idea re-introduced the atomic idea to modern chemistry to modern chemistry
Dalton and other chemists Dalton and other chemists did experiments involving did experiments involving gases and how they combinegases and how they combine
They noticed that elements They noticed that elements always seemed to combine always seemed to combine in the same ratios (in the same ratios (such as such as 1:1, 1:2, 2:3 etc)1:1, 1:2, 2:3 etc)
DaltonDalton’’s Atom, 1807s Atom, 1807 To explain these observations, Dalton To explain these observations, Dalton
hypothesized that:hypothesized that: Chemical elements are made of atoms Chemical elements are made of atoms The atoms of the same element have the same The atoms of the same element have the same
massmass Atoms of different elements have different Atoms of different elements have different
masses (but the same general shape)masses (but the same general shape) Atoms are involved in chemical reactions but are
not changed by them Characteristics of Dalton’s atom
uniformly dense indivisible solid spheres
The Thomson ModelThe Thomson Model1897: J.J. Thomson hypothesized that 1897: J.J. Thomson hypothesized that
there are areas of negative charge there are areas of negative charge (electrons) within the atom(electrons) within the atom
Based on experimental observationsBased on experimental observationsCalled the Plum Pudding ModelCalled the Plum Pudding Model
Discovery of the ElectronDiscovery of the Electron
http://www.youtube.com/watch?v=IdTxGJjA4Jw
RutherfordRutherford’’s Gold Foil Experiments Gold Foil Experiment Rutherford shot alpha particles at gold foil expected the alpha particles to go through the gold
foil but be deflected- most particles did Some alpha particles weren’t deflected, they
bounced back! He said “It was almost as incredible as if you fired a
15-inch shell at a piece of tissue paper and it came back and hit you."
The Rutherford Model, 1911The Rutherford Model, 1911 Atomic theory was revised to explain RutherforAtomic theory was revised to explain Rutherfor
dd’’s observations s observations RutherfordRutherford’’s Model stated:s Model stated:
The atom contains a tiny dense center called the The atom contains a tiny dense center called the nucleus nucleus
the volume of the nucleus is about 1/10 trillionth the the volume of the nucleus is about 1/10 trillionth the volume of the atom volume of the atom
The nucleus is essentially the entire mass of the The nucleus is essentially the entire mass of the atom (the rest is mostly empty space)atom (the rest is mostly empty space)
The Rutherford Model, 1911The Rutherford Model, 1911
RutherfordRutherford’’s Model stated:s Model stated:The nucleus is positively chargedThe nucleus is positively chargedThe amount of positive charge of the nucleus The amount of positive charge of the nucleus
balances the negative charge of the electrons balances the negative charge of the electrons The electrons move around in The electrons move around in
the empty space of the atom the empty space of the atom
surrounding the nucleussurrounding the nucleus 3p+
e-
e-e-
Discovery of the NucleusDiscovery of the Nucleus
http://www.youtube.com/watch?v=wzALbzTdnc8 http://www.youtube.com/watch?v=wzALbzTdnc8
The Bohr ModelThe Bohr Model
Niels Bohr Niels Bohr applies quantum theory to applies quantum theory to
Rutherford's atomic structureRutherford's atomic structure led to the idea of electrons led to the idea of electrons
moving around the nucleus in moving around the nucleus in orbits or energy levelsorbits or energy levels
emission of light occurs when emission of light occurs when an electron moves into a an electron moves into a lower energy orbit.lower energy orbit.
BohrBohr’’s Researchs Research Electron orbit around the nucleus in seven different Electron orbit around the nucleus in seven different
energy levels, or shells. energy levels, or shells. Electrons would only occupy the lowest possible Electrons would only occupy the lowest possible
energy level.energy level. Electrons would only move up a level (increasing Electrons would only move up a level (increasing
energy) if the lower levels were full.energy) if the lower levels were full.
Atomic ScaleAtomic Scale
Modern Atomic TheoryModern Atomic Theory
An updated version of BohrAn updated version of Bohr’’s models modelElectrons move in 3-D clouds rather than Electrons move in 3-D clouds rather than
orbitsorbitsThere are three There are three
types of particles types of particles
in the atom rather in the atom rather
than twothan two
Subatomic ParticlesSubatomic ParticlesParticle Particle ChargeCharge Mass (kg)Mass (kg) Relative Relative
MassMassLocationLocation
Subatomic ParticlesSubatomic ParticlesParticle Particle ChargeCharge Mass (kg)Mass (kg) Relative Relative
MassMassLocationLocation
ProtonProton
NeutronNeutron
ElectronElectron
Subatomic ParticlesSubatomic ParticlesParticle Particle ChargeCharge Mass (kg)Mass (kg) Relative Relative
MassMassLocationLocation
ProtonProton 11
NeutronNeutron
ElectronElectron
Subatomic ParticlesSubatomic ParticlesParticle Particle ChargeCharge Mass (kg)Mass (kg) Relative Relative
MassMassLocationLocation
ProtonProton 11
NeutronNeutron 00
ElectronElectron
Subatomic ParticlesSubatomic ParticlesParticle Particle ChargeCharge Mass (kg)Mass (kg) Relative Relative
MassMassLocationLocation
ProtonProton 11
NeutronNeutron 00
ElectronElectron -1-1
Subatomic ParticlesSubatomic ParticlesParticle Particle ChargeCharge Mass (kg)Mass (kg) Relative Relative
MassMassLocationLocation
ProtonProton 11 1.67x101.67x10-27-27 11
NeutronNeutron 00 1.67x101.67x10-27-27
ElectronElectron -1-1 9.11x109.11x10-31-31
Subatomic ParticlesSubatomic ParticlesParticle Particle ChargeCharge Mass (kg)Mass (kg) Relative Relative
MassMassLocationLocation
ProtonProton 11 1.67x101.67x10-27-27 11
NeutronNeutron 00 1.67x101.67x10-27-27 11
ElectronElectron -1-1 9.11x109.11x10-31-31
Subatomic ParticlesSubatomic ParticlesParticle Particle ChargeCharge Mass (kg)Mass (kg) Relative Relative
MassMassLocationLocation
ProtonProton 11 1.67x101.67x10-27-27 11
NeutronNeutron 00 1.67x101.67x10-27-27 11
ElectronElectron -1-1 9.11x109.11x10-31-31 00
Subatomic ParticlesSubatomic ParticlesParticle Particle ChargeCharge Mass (kg)Mass (kg) Relative Relative
MassMassLocationLocation
ProtonProton 11 1.67x101.67x10-27-27 11 NucleusNucleus
NeutronNeutron 00 1.67x101.67x10-27-27 11
ElectronElectron -1-1 9.11x109.11x10-31-31 00
Subatomic ParticlesSubatomic ParticlesParticle Particle ChargeCharge Mass (kg)Mass (kg) Relative Relative
MassMassLocationLocation
ProtonProton 11 1.67x101.67x10-27-27 11 NucleusNucleus
NeutronNeutron 00 1.67x101.67x10-27-27 11 NucleusNucleus
ElectronElectron -1-1 9.11x109.11x10-31-31 00
Subatomic ParticlesSubatomic ParticlesParticle Particle ChargeCharge Mass (kg)Mass (kg) Relative Relative
MassMassLocationLocation
ProtonProton 11 1.67x101.67x10-27-27 11 NucleusNucleus
NeutronNeutron 00 1.67x101.67x10-27-27 11 NucleusNucleus
ElectronElectron -1-1 9.11x109.11x10-31-31 00 outside outside nucleusnucleus
http://abyss.uoregon.edu/~js/http://abyss.uoregon.edu/~js/21st_century_science/lectures/lec05.html21st_century_science/lectures/lec05.html
http://dl.clackamas.edu/ch104-04/daltonhttp://dl.clackamas.edu/ch104-04/dalton%27s.htm%27s.htm
http://abyss.uoregon.edu/~js/http://abyss.uoregon.edu/~js/21st_century_science/lectures/lec11.html21st_century_science/lectures/lec11.html
http://galileo.phys.virginia.edu/classes/http://galileo.phys.virginia.edu/classes/252/Rutherford_Scattering/252/Rutherford_Scattering/Rutherford_Scattering.html Rutherford_Scattering.html