Atoms, Elements and Atoms, Elements and Quantum MechanicsQuantum Mechanics

01 and 06 October 201501 and 06 October 2015

PhysicsPhysics

ChemistryChemistry AstronomyAstronomy

Geology/EcologyGeology/Ecology

BiologyBiology

TopicsTopics

Discovery of atomic structure and Discovery of atomic structure and functionfunction

Models of atomsModels of atoms Thompson and Rutherford atom (~1900)Thompson and Rutherford atom (~1900) Bohr atom (1913)Bohr atom (1913) Quantum mechanics (1930’s)Quantum mechanics (1930’s)

Elements, atoms and the Periodic TableElements, atoms and the Periodic Table Electrons in orbits nested within shellsElectrons in orbits nested within shells Valence electronsValence electrons

Some Notations on the Some Notations on the SyllabusSyllabus

DeleteDelete: : Chemical reactions (pp. 223-Chemical reactions (pp. 223-227)227)

Chapter 11: Materials and Chapter 11: Materials and PropertiesProperties

(pp. 237-259)(pp. 237-259)

Crystal Morphology and Crystal Morphology and Color: Structure of the Color: Structure of the

AtomAtom

Leaf Color:Leaf Color:Structure of the AtomStructure of the Atom

Eye Color:Eye Color:Structure of the AtomStructure of the Atom

Compounds to Quarks:Compounds to Quarks: A Hierarchy A Hierarchy

CompoundCompound

ElementElement

AtomAtom

Subatomic Subatomic ParticleParticle

Quarks Quarks (Higgs)(Higgs)Hierarchy theory and emergent

properties

Thompson’s Investigation of Thompson’s Investigation of the Electron (1870’s)the Electron (1870’s)

Idea: smaller components comprise Idea: smaller components comprise atomsatoms

HypothesisHypothesis: Atoms consist of : Atoms consist of components, one of which is components, one of which is negatively charged with a very negatively charged with a very small masssmall mass

Testing the hypothesisTesting the hypothesis

Thompson’s ExperimentThompson’s Experiment

Observations:

1. Deflection of negatively- charged beam

2. Very small mass

3. Mass same for all elements

Hypothesis: Accept

Particle name: Electron

Methodology

HypothesisHypothesis:: Atoms consist of components, one Atoms consist of components, one of which is of which is negatively charged with a negatively charged with a very small massvery small mass

Rutherford’s Investigation Rutherford’s Investigation of the Nucleus (1910)of the Nucleus (1910)

Idea: other smaller components are part of atoms Idea: other smaller components are part of atoms too, including ones that are positively chargedtoo, including ones that are positively charged

HypothesisHypothesis: Atoms consist of multiple : Atoms consist of multiple subcomponents, one of which is positive in subcomponents, one of which is positive in chargecharge

Testing the hypothesisTesting the hypothesis Alpha particles (+), gold foil, “bullets”, and “tracks”Alpha particles (+), gold foil, “bullets”, and “tracks”

http://www.youtube.com/watch?v=5pZj0u_XMbc

Observations, Hypothesis, Observations, Hypothesis, Conclusion and a Revised Conclusion and a Revised

ModelModel ObservationsObservations Almost all alpha’s (+) passed through foil unaffectedAlmost all alpha’s (+) passed through foil unaffected Very small number of alpha’s (+) deflected at a small angleVery small number of alpha’s (+) deflected at a small angle 1/1,000 bounced back1/1,000 bounced back

HypothesisHypothesis: Atom consists of a (i) : Atom consists of a (i) positivepositive component that is (ii) component that is (ii) smallsmall in volume in in volume in comparison to atom itselfcomparison to atom itself

Accept/reject?Accept/reject?

ConclusionsConclusions Name of particle is the Name of particle is the protonproton ElectronsElectrons circling the nucleus circling the nucleus

Shortcomings of the new model?Shortcomings of the new model?

Resolving Shortcoming of Resolving Shortcoming of the Model: Atomic the Model: Atomic

Structure and the Bohr Structure and the Bohr AtomAtom Observations (1913)Observations (1913)

Heat hydrogen gas and light emitted as a Heat hydrogen gas and light emitted as a discretediscrete wavelengths (not continuous spectrum)wavelengths (not continuous spectrum)

Other gases behave the same in producing discrete Other gases behave the same in producing discrete wavelengthwavelength

ButBut, each gas is unique in each gas is unique in

emitted (e.g., violet versus emitted (e.g., violet versus

yellow versus red versus yellow versus red versus

green)green)

Bohr’s Hypothesis and Bohr’s Hypothesis and ModelModel

Quantum Concepts

1. Only discrete orbits for electrons

2. Discrete frequency of photon (emitted light)

3. Explains spectroscopic properties ofelements

Quantum Behavior and Quantum Behavior and SpectroscopySpectroscopy

Application of Application of Spectroscopy: Elemental Spectroscopy: Elemental

AnalysisAnalysis

Bohr’s Model of the Bohr’s Model of the AtomAtom

Building on predecessor models:Building on predecessor models: Thompson’s electronThompson’s electron Rutherford’s nucleus and protonsRutherford’s nucleus and protons

Electrons in orbitsElectrons in orbits Orbits exhibit discrete Orbits exhibit discrete quantum quantum

structure/layersstructure/layers When excited, electrons release energy in When excited, electrons release energy in

discrete packets of energy (discrete packets of energy (photons of lightphotons of light))

Sequel to Bohr’s atom (2-3 decades): Sequel to Bohr’s atom (2-3 decades): quantum mechanicsquantum mechanics

Bohr’s Atom and Bohr’s Atom and SpectroscopySpectroscopy

QuestionQuestion

The science of spectroscopy examines the nature of ___ emitted from excited atoms.

A. ElectronsB. ProtonsC. PhotonsD. NeutronsE. Galileons

QuestionQuestion

The negatively charged particle that is part of an atom is the ___.

A. PhotonB. NeutronC. ProtonD. Electron

Electrons as Particles and Electrons as Particles and Waves: Wave-Particle Waves: Wave-Particle

DualityDuality(Moving Toward Quantum (Moving Toward Quantum

Mechanics)Mechanics)

http://

www.youtube.com/watch?v=DfPeprQ7oGc

TheoryTheory of Quantum of Quantum MechanicsMechanics

ObservationsObservations Quantum behavior of Quantum behavior of

electrons in Bohr model electrons in Bohr model (orbits, etc.)(orbits, etc.)

Wave-particle duality of Wave-particle duality of electrons electrons

Key: integrated mechanisms of Key: integrated mechanisms of waves and particles, focusing waves and particles, focusing on “fuzzy electron clouds”on “fuzzy electron clouds”

HypothesisHypothesis:: new evolving new evolving model of atomic structure: model of atomic structure: quantum mechanics quantum mechanics theorytheory of of the atomthe atom Incorporation of parts of Incorporation of parts of

predecessorpredecessor Plus: wave properties of Plus: wave properties of

electrons in orbitselectrons in orbits

According to the Rutherford model of the atom, the volume of any atom is largely _______.

A. protons and neutronsB. electronsC. empty spaceD. noxiously sequenced nuons

surrounded by pompous protons

E. none of the above

QuestionQuestion

The existence of a tiny, positively charged atomic nucleus was deduced from the observation that ___.

A. fast, massive, and positively charged alpha particles

move in straight lines through gold foil

B. alpha particles were deflected by a magnetic field

C. some (very few) alpha particles were deflected by metal foil

D. all of the aboveE. A and C

QuestionQuestion

According to the Bohr model of the atom, an electron gains or looses energy only by ______.

A. jumping from one atom to anotherB. speeding up or slowing down in its orbitC. jumping from one orbit to anotherD. being removed from the atom

QuestionQuestion

QuestionQuestion

The double-slit experiment was most important in documenting ___.

A. The small uncertainty of large objectsB. The large uncertainty of small objectsC. The wave-particle dualityD. The Heisenberg principle

TopicsTopics

Discovery of atomic structure and Discovery of atomic structure and functionfunction

Models of atomsModels of atoms Thompson and Rutherford atomsThompson and Rutherford atoms Bohr atom (1913)Bohr atom (1913) Quantum mechanics (1930’s)Quantum mechanics (1930’s)

Elements, atoms and the Periodic TableElements, atoms and the Periodic Table Electrons in orbits nested within shells Electrons in orbits nested within shells Valence electronsValence electrons

ElementsElements

PatternsPatterns 92 naturally occurring elements (e.g., hydrogen, 92 naturally occurring elements (e.g., hydrogen,

gold, helium)gold, helium) Total of 118+Total of 118+ 25 of 92 are essential to life (e.g., what are they?)25 of 92 are essential to life (e.g., what are they?)

Key pointsKey points any element is the same in its chemical structure any element is the same in its chemical structure

and physical properties (stable over time, with one and physical properties (stable over time, with one exception - radioactive elements)exception - radioactive elements)

AllAll elements have origin in either the big bang elements have origin in either the big bang (hydrogen and helium) or the subsequent evolution (hydrogen and helium) or the subsequent evolution of the universe (Dr. Geller will speak to this a bit of the universe (Dr. Geller will speak to this a bit later)later)

Atomic No Symbol Name

1 H Hydrogen2 He Helium

6 C Carbon7 N Nitrogen8 O Oxygen

17 Cl Chlorine18 Ar Argon

26 Fe Iron53 I Iodine

79 Au Gold80 Hg Mercury

94 Pu Plutonium104 RfRutherfordium

TopicsTopics

Discovery of atomic structure and Discovery of atomic structure and functionfunction

Models of atomsModels of atoms Thompson and Rutherford atomsThompson and Rutherford atoms Bohr atom (1913)Bohr atom (1913) Quantum mechanics (1930’s)Quantum mechanics (1930’s)

Elements, atoms and the Periodic TableElements, atoms and the Periodic Table Electrons in orbits nested within shells Electrons in orbits nested within shells Valence electronsValence electrons

Elements and CompoundsElements and Compounds Compound (combinations of atoms)Compound (combinations of atoms)

Elements combine in recurrent, precise and Elements combine in recurrent, precise and predictable wayspredictable ways

Sodium + Chlorine = Sodium ChlorideSodium + Chlorine = Sodium Chloride NaNa + Cl =+ Cl = NaClNaClmetal + gas = solidmetal + gas = solid

Key points Key points Atoms of sodium (Na) and chlorine (Cl) remain Atoms of sodium (Na) and chlorine (Cl) remain

atoms of each respective elementatoms of each respective element Product (NaCl) is recurrent and predictableProduct (NaCl) is recurrent and predictable EmergentEmergent propertyproperty: “emergence” of new : “emergence” of new

properties in a compound not predicted by the properties in a compound not predicted by the summation of the two elements (summation of the two elements (hierarchy hierarchy theorytheory))

Other example: Hydrogen + oxygen = __________Other example: Hydrogen + oxygen = __________

Subatomic ParticlesSubatomic Particles

Atoms composed of subatomic particlesAtoms composed of subatomic particles Most stable particlesMost stable particles

NeutronsNeutrons ProtonsProtons ElectronsElectrons

Other less stable and understood particles (quarks, Other less stable and understood particles (quarks, neutrinos, etc. … Dr. Geller will speak to this later)neutrinos, etc. … Dr. Geller will speak to this later)

Relationship among the more stable particlesRelationship among the more stable particles

NeutronNeutron ProtonProton ElectronElectronChargeCharge neutralneutral positivepositive negativenegativeMassMass 2 x 102 x 10-24-24 g g 2 x 102 x 10-24-24 g g 5 x 5 x

1010--2828 g g

What is Right About this Model?

What is Not Right About this Model?

Electrons in Orbits

ElectronsElectrons

Energy “Energy “baronsbarons” of the ” of the atom (motion and in orbits) atom (motion and in orbits) Energy = ability to do Energy = ability to do

workwork Potential energy = Potential energy =

energy stored due to energy stored due to position or location (i.e., position or location (i.e., orbits)orbits)

Charge is negative (-) and Charge is negative (-) and particle is “in motion” in a particle is “in motion” in a quantum sensequantum sense

Key to Electron StructureKey to Electron Structure

Count the number of protons: number of Count the number of protons: number of electrons = number of protons (why?)electrons = number of protons (why?)

Electrons are negative in charge and act Electrons are negative in charge and act as particles as particles andand waves in a quantum waves in a quantum sensesense

Electrons are in motion around the Electrons are in motion around the nucleus in “orbits” that are discretenucleus in “orbits” that are discrete

Only two electrons exist in a given orbit Only two electrons exist in a given orbit (Pauli’s Exclusion Principle)(Pauli’s Exclusion Principle)

ElectronsElectrons

Example of Sulfur (Example of Sulfur (16163232S)S)

(16 electrons in 3 shells)(16 electrons in 3 shells)

What are shells, what are orbits and who is Pauli?

Orbits, Shells and Orbits, Shells and ElectronsElectrons

http://www.colorado.edu/physics/2000/applets/a2.html

Example of Electrons in Example of Electrons in ShellsShells

As electrons move among shells, they change As electrons move among shells, they change potential energypotential energy Hot summer day, bright sun and car topHot summer day, bright sun and car top

Light absorption by pigments and electrons “jump” to Light absorption by pigments and electrons “jump” to higher shell (potential energy); give off energy when higher shell (potential energy); give off energy when they drop back (kinetic/heat energy)they drop back (kinetic/heat energy)

Banana, orange juice or bagel this AM (how Banana, orange juice or bagel this AM (how about a granola bar)?about a granola bar)?

Excited electron “captured” by chlorophyll in leaf and Excited electron “captured” by chlorophyll in leaf and shuttled to a sugar molecule in its excited state shuttled to a sugar molecule in its excited state (potential energy) until you release the energy (potential energy) until you release the energy viavia digestion, allowing the electron to “drop back” to a digestion, allowing the electron to “drop back” to a lower orbit (kinetic/chemical/heat energy)lower orbit (kinetic/chemical/heat energy)

Some Keys to Electron Some Keys to Electron StructureStructure

Electrons reside in shells as a function of Electrons reside in shells as a function of quantum mechanics (1-4 orbits per shell)quantum mechanics (1-4 orbits per shell)

Never more than two electrons per orbit Never more than two electrons per orbit (Pauli’s Exclusion Principle)(Pauli’s Exclusion Principle)

Distribution of electrons is key to Distribution of electrons is key to understanding why elements and atoms understanding why elements and atoms behave the way they dobehave the way they do

Outermost electrons are called Outermost electrons are called valence valence electrons; electrons; special significance in chemistryspecial significance in chemistry

Periodic Table of ElementsPeriodic Table of Elements

Concept: most stable state for an atom Concept: most stable state for an atom = outermost shell filled with maximum = outermost shell filled with maximum number of electronsnumber of electrons

11stst Shell (1 orbit; 2 electrons) Shell (1 orbit; 2 electrons) Hydrogen (Hydrogen (11

11H; 1 electron; stable ?)H; 1 electron; stable ?)

Helium (Helium (2244He; 2 electrons; stable ?)He; 2 electrons; stable ?)

Periodic Table’s 1Periodic Table’s 1stst Row Row Hydrogen and HeliumHydrogen and Helium

Orbits, Shells and Orbits, Shells and ElectronsElectrons

http://www.colorado.edu/physics/2000/applets/a2.html

Atomic Structure: Periodic Atomic Structure: Periodic TableTable

Unstable Stable

Periodic TablePeriodic Table

Periodic Table of ElementsPeriodic Table of Elements

22ndnd shell has 4 orbits with 2 electrons shell has 4 orbits with 2 electrons (maximum) per orbit (total of 8 (maximum) per orbit (total of 8 electrons/shell)electrons/shell)

Most stable configuration is:Most stable configuration is: 11stst shell filled with 2 electrons shell filled with 2 electrons 22ndnd shell filled with 8 electrons shell filled with 8 electrons Total of 10 electrons (Total of 10 electrons (1010

2020Ne)Ne)

22ndnd row of Periodic Table row of Periodic Table 8 elements8 elements

Periodic Table of ElementsPeriodic Table of Elements

Number of elements in a row is not Number of elements in a row is not chance; reflects the maximum number chance; reflects the maximum number of electrons in the outermost shellof electrons in the outermost shell

Row 1 Row 1 << 2 2 Row 2 Row 2 << 8 (plus Row 1) 8 (plus Row 1) Row 3 Row 3 << 8 (plus Row 1 + Row 2) ) 8 (plus Row 1 + Row 2) ) Row 4 Row 4 << 18 (plus Row 1 + Row2 + Row 3) 18 (plus Row 1 + Row2 + Row 3) Etc.Etc.

Periodic Table as a Periodic Table as a “Model”“Model”

Models = conceptual and/or mathematical Models = conceptual and/or mathematical expressions that help scientists understand expressions that help scientists understand how the natural world operateshow the natural world operates

Models foster predictions about how the Models foster predictions about how the natural world operatenatural world operate Model of the structure of the atom predicts …Model of the structure of the atom predicts … Your model of your family dynamic predicts …Your model of your family dynamic predicts …

Periodic table predicts that unknown Periodic table predicts that unknown “elements” have specific physical and “elements” have specific physical and chemical propertieschemical properties

Predictive Value of the Predictive Value of the Periodic TablePeriodic Table

??

In the list below, an atom of _______ has the greatest ability to attract electrons.

A. siliconB. sulfurC. kryptonD. chlorineE. sodium

Question (walk through)Question (walk through)

In the list below, an atom of _______ has the least ability to attract electrons.

A. siliconB. sulfurC. kryptonD. chlorineE. sodium

QuestionQuestion

QuestionQuestion

In the Periodic Table, carbon is element #6. This means it has six electrons. How many valence electrons does carbon have?

A. 1B. 2C. 3D. 4E. 8

QuestionQuestion

In the Periodic Table, neon is element # 10. How many electrons does neon have in its outermost electron shell?

A. 2B. 4C. 6D. 8

TopicsTopics

Discovery of atomic structure and Discovery of atomic structure and functionfunction

Models of atomsModels of atoms Thompson and Rutherford atom (~1900)Thompson and Rutherford atom (~1900) Bohr atom (1913)Bohr atom (1913) Quantum mechanics (1930’s)Quantum mechanics (1930’s)

Elements, atoms and the Periodic TableElements, atoms and the Periodic Table Electrons in orbits nested within shellsElectrons in orbits nested within shells Valence electronsValence electrons

Atoms, Elements and Atoms, Elements and Quantum MechanicsQuantum Mechanics

01 and 06 October 201501 and 06 October 2015

PhysicsPhysics

ChemistryChemistry AstronomyAstronomy

Geology/EcologyGeology/Ecology

BiologyBiology