Atoms, Elements and Quantum Mechanics 01 and 06 October 2015 Physics Chemistry Chemistry Astronomy Astronomy Geology/Ecology Geology/Ecology Biology Biology

Topics Discovery of atomic structure and function Discovery of atomic structure and function Models of atoms Models 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 Table Elements, atoms and the Periodic Table Electrons in orbits nested within shells Electrons in orbits nested within shells Valence electrons Valence electrons

Some Notations on the Syllabus Delete: Chemical reactions (pp ) Delete: Chemical reactions (pp ) Chapter 11: Materials and Properties (pp )

Crystal Morphology and Color: Structure of the Atom

Leaf Color: Structure of the Atom

Eye Color: Structure of the Atom

Compounds to Quarks: A Hierarchy CompoundElement Atom Atom Subatomic Particle Subatomic Particle Quarks (Higgs) Quarks (Higgs) Hierarchy theory and emergent properties

Thompson’s Investigation of the Electron (1870’s) Idea: smaller components comprise atoms Idea: smaller components comprise atoms Hypothesis: Atoms consist of components, one of which is negatively charged with a very small mass Hypothesis: Atoms consist of components, one of which is negatively charged with a very small mass Testing the hypothesis Testing the hypothesis

Thompson’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 Hypothesis: Atoms consist of components, one of which is negatively charged with a very small mass

Rutherford’s Investigation of the Nucleus (1910) Idea: other smaller components are part of atoms too, including ones that are positively charged Idea: other smaller components are part of atoms too, including ones that are positively charged Hypothesis: Atoms consist of multiple subcomponents, one of which is positive in charge Hypothesis: Atoms consist of multiple subcomponents, one of which is positive in charge Testing the hypothesis Testing the hypothesis Alpha particles (+), gold foil, “bullets”, and “tracks” Alpha particles (+), gold foil, “bullets”, and “tracks”

Observations, Hypothesis, Conclusion and a Revised Model Observations Observations Almost all alpha’s (+) passed through foil unaffected Almost all alpha’s (+) passed through foil unaffected Very small number of alpha’s (+) deflected at a small angle Very small number of alpha’s (+) deflected at a small angle 1/1,000 bounced back 1/1,000 bounced back Hypothesis : Atom consists of a (i) positive component that is (ii) small in volume in comparison to atom itself Hypothesis : Atom consists of a (i) positive component that is (ii) small in volume in comparison to atom itself Accept/reject? Accept/reject? Conclusions Conclusions Name of particle is the proton Name of particle is the proton Electrons circling the nucleus Electrons circling the nucleus Shortcomings of the new model? Shortcomings of the new model?

Resolving Shortcoming of the Model: Atomic Structure and the Bohr Atom Observations (1913) Observations (1913) Heat hydrogen gas and light emitted as a discrete wavelengths (not continuous spectrum) Heat hydrogen gas and light emitted as a discrete wavelengths (not continuous spectrum) Other gases behave the same in producing discrete wavelength Other gases behave the same in producing discrete wavelength But each gas is unique in But, each gas is unique in emitted (e.g., violet versus yellow versus red versus green) green)

Bohr’s Hypothesis and Model Quantum Concepts 1. Only discrete orbits for electrons 2. Discrete frequency of photon (emitted light) 3. Explains spectroscopic properties ofelements

Quantum Behavior and Spectroscopy

Application of Spectroscopy: Elemental Analysis

Bohr’s Model of the Atom Building on predecessor models: Building on predecessor models: Thompson’s electron Thompson’s electron Rutherford’s nucleus and protons Rutherford’s nucleus and protons Electrons in orbits Electrons in orbits Orbits exhibit discrete quantum structure/layers Orbits exhibit discrete quantum structure/layers When excited, electrons release energy in discrete packets of energy (photons of light) When excited, electrons release energy in discrete packets of energy (photons of light) Sequel to Bohr’s atom (2-3 decades): quantum mechanics Sequel to Bohr’s atom (2-3 decades): quantum mechanics

Bohr’s Atom and Spectroscopy

Electrons as Particles and Waves: Wave-Particle Duality h ttp://

Theory of Quantum Mechanics Observations Observations Quantum behavior of electrons in Bohr model (orbits, etc.) Quantum behavior of electrons in Bohr model (orbits, etc.) Wave-particle duality of electrons Wave-particle duality of electrons Key: integrated mechanisms of waves and particles, focusing on “fuzzy electron clouds” Key: integrated mechanisms of waves and particles, focusing on “fuzzy electron clouds” Hypothesis: new evolving model of atomic structure: quantum mechanics theory of the atom Hypothesis: new evolving model of atomic structure: quantum mechanics theory of the atom Incorporation of parts of predecessor Incorporation of parts of predecessor Plus: wave properties of electrons in orbits Plus: wave properties of electrons in orbits

Topics Discovery of atomic structure and function Discovery of atomic structure and function Models of atoms Models of atoms Thompson and Rutherford atoms Thompson and Rutherford atoms Bohr atom (1913) Bohr atom (1913) Quantum mechanics (1930’s) Quantum mechanics (1930’s) Elements, atoms and the Periodic Table Elements, atoms and the Periodic Table Electrons in orbits nested within shells Electrons in orbits nested within shells Valence electrons Valence electrons

Elements Patterns Patterns 92 naturally occurring elements (e.g., hydrogen, gold, helium) 92 naturally occurring elements (e.g., hydrogen, gold, helium) Total of 113+ Total of of 92 are essential to life (e.g., what are they?) 25 of 92 are essential to life (e.g., what are they?) Key points Key points any element is the same in its chemical structure and physical properties (stable over time, with one exception - radioactive elements) any element is the same in its chemical structure and physical properties (stable over time, with one exception - radioactive elements) All elements have origin in either the big bang (hydrogen and helium) or the subsequent evolution of the universe (Dr. Geller will speak to this a bit later) All elements have origin in either the big bang (hydrogen and helium) or the subsequent evolution of the universe (Dr. Geller will speak to this a bit later)

Atomic NoSymbolName 1HHydrogen 2HeHelium 6CCarbon 7NNitrogen 8OOxygen 17ClChlorine 18ArArgon 26FeIron 53IIodine 79AuGold 80HgMercury 94PuPlutonium 104RfRutherfordium

Topics Discovery of atomic structure and function Discovery of atomic structure and function Models of atoms Models of atoms Thompson and Rutherford atoms Thompson and Rutherford atoms Bohr atom (1913) Bohr atom (1913) Quantum mechanics (1930’s) Quantum mechanics (1930’s) Elements, atoms and the Periodic Table Elements, atoms and the Periodic Table Electrons in orbits nested within shells Electrons in orbits nested within shells Valence electrons Valence electrons

Elements and Compounds Compound Compound Elements combine in recurrent, precise and predictable ways Elements combine in recurrent, precise and predictable ways Sodium + Chlorine = Sodium Chloride Sodium + Chlorine = Sodium Chloride Na+ Cl = NaCl Na+ Cl = NaCl metal + gas = solid Key points Key points Atoms of sodium (Na) and chlorine (Cl) remain atoms of each respective element Atoms of sodium (Na) and chlorine (Cl) remain atoms of each respective element Product (NaCl) is recurrent and predictable Product (NaCl) is recurrent and predictable Emergent property: “emergence” of new properties in a compound not predicted by the summation of the two elements (hierarchy theory) Emergent property: “emergence” of new properties in a compound not predicted by the summation of the two elements (hierarchy theory) Other example: Hydrogen + oxygen = __________ Other example: Hydrogen + oxygen = __________

Subatomic Particles Atoms composed of subatomic particles Atoms composed of subatomic particles Most stable particles Most stable particles Neutrons Neutrons Protons Protons Electrons Electrons Other less stable and understood particles (quarks, etc. … Dr. Geller will speak to this later) Other less stable and understood particles (quarks, etc. … Dr. Geller will speak to this later) Relationship among the more stable particles Relationship among the more stable particles Neutron ProtonElectron Chargeneutralpositivenegative Mass 2 x g 2 x g 5 x g

What is Right About this Model? What is Not Right About this Model?

Electrons in Orbits

Electrons Energy “barons” of the atom (motion and in orbits) Energy “barons” of the atom (motion and in orbits) Energy = ability to do work Energy = ability to do work Potential energy = energy stored due to position or location (i.e., orbits) Potential energy = energy stored due to position or location (i.e., orbits) Charge is negative (-) and particle is “in motion” in a quantum sense Charge is negative (-) and particle is “in motion” in a quantum sense

Key to Electron Structure Count the number of protons: number of electrons = number of protons (why?) Count the number of protons: number of electrons = number of protons (why?) Electrons are negative in charge and act as particles and waves in a quantum sense Electrons are negative in charge and act as particles and waves in a quantum sense Electrons are in motion around the nucleus in “orbits” that are discrete Electrons are in motion around the nucleus in “orbits” that are discrete Only two electrons exist in a given orbit (Pauli’s Exclusion Principle) Only two electrons exist in a given orbit (Pauli’s Exclusion Principle)

Electrons Example of Sulfur ( S) Example of Sulfur ( S) (16 electrons in 3 shells) What are shells, what are orbits and who is Pauli?

Orbits, Shells and Electrons

Example of Electrons in Shells As electrons move among shells, they change potential energy Hot summer day, bright sun and car top Hot summer day, bright sun and car top Light absorption by pigments and electrons “jump” to higher shell (potential energy); give off energy when they drop back (kinetic/heat energy) Light absorption by pigments and electrons “jump” to higher shell (potential energy); give off energy when they drop back (kinetic/heat energy) Banana, orange juice or bagel this AM (how about a granola bar)? Banana, orange juice or bagel this AM (how about a granola bar)? Excited electron “captured” by chlorophyll in leaf and shuttled to a sugar molecule in its excited state (potential energy) until you release the energy via digestion, allowing the electron to “drop back” to a lower orbit (kinetic/chemical/heat energy) Excited electron “captured” by chlorophyll in leaf and shuttled to a sugar molecule in its excited state (potential energy) until you release the energy via digestion, allowing the electron to “drop back” to a lower orbit (kinetic/chemical/heat energy)

Some Keys to Electron Structure Electrons reside in shells as a function of quantum mechanics (1-4 orbits per shell) Electrons reside in shells as a function of quantum mechanics (1-4 orbits per shell) Never more than two electrons per orbit (Pauli’s Exclusion Principle) Never more than two electrons per orbit (Pauli’s Exclusion Principle) Distribution of electrons is key to understanding why elements and atoms behave the way they do Distribution of electrons is key to understanding why elements and atoms behave the way they do Outermost electrons are called valence electrons; special significance in chemistry Outermost electrons are called valence electrons; special significance in chemistry

Periodic Table of Elements Concept: most stable state for an atom = outermost shell filled with maximum number of electrons Concept: most stable state for an atom = outermost shell filled with maximum number of electrons 1 st Shell (1 orbit; 2 electrons) 1 st Shell (1 orbit; 2 electrons) Hydrogen ( 1 1 H; 1 electron; stable ?) Hydrogen ( 1 1 H; 1 electron; stable ?) Helium ( 2 4 He; 2 electrons; stable ?) Helium ( 2 4 He; 2 electrons; stable ?) Periodic Table’s 1 st Row Periodic Table’s 1 st Row Hydrogen and Helium Hydrogen and Helium

Orbits, Shells and Electrons

Atomic Structure: Periodic Table Unstable Stable

Periodic Table

Periodic Table of Elements 2 nd shell has 4 orbits with 2 electrons (maximum) per orbit (total of 8 electrons/shell) 2 nd shell has 4 orbits with 2 electrons (maximum) per orbit (total of 8 electrons/shell) Most stable configuration is: Most stable configuration is: 1 st shell filled with 2 electrons 1 st shell filled with 2 electrons 2 nd shell filled with 8 electrons 2 nd shell filled with 8 electrons Total of 10 electrons ( Ne) Total of 10 electrons ( Ne) 2 nd row of Periodic Table 2 nd row of Periodic Table 8 elements 8 elements

Periodic Table of Elements Number of elements in a row is not chance; reflects the maximum number of electrons in the outermost shell Number of elements in a row is not chance; reflects the maximum number of electrons in the outermost shell Row 1 < 2 Row 1 < 2 Row 2 < 8 (plus Row 1) Row 2 < 8 (plus Row 1) Row 3 < 8 (plus Row 1 + Row 2) ) Row 3 < 8 (plus Row 1 + Row 2) ) Row 4 < 18 (plus Row 1 + Row2 + Row 3) Row 4 < 18 (plus Row 1 + Row2 + Row 3) Etc. Etc.

Periodic Table as a “Model” Models = conceptual and/or mathematical expressions that help scientists understand how the natural world operates Models = conceptual and/or mathematical expressions that help scientists understand how the natural world operates Models foster predictions about how the natural world operate Models foster predictions about how the natural 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 “elements” have specific physical and chemical properties Periodic table predicts that unknown “elements” have specific physical and chemical properties

Predictive Value of the Periodic Table ? ?

Question In the Periodic Table, neon is element # 10. How many electrons does neon have in its outermost electron shell? A.2 B.4 C.6 D.8

Topics Discovery of atomic structure and function Discovery of atomic structure and function Models of atoms Models 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 Table Elements, atoms and the Periodic Table Electrons in orbits nested within shells Electrons in orbits nested within shells Valence electrons Valence electrons

Atoms, Elements and Quantum Mechanics 01 and 06 October 2015 Physics Chemistry Chemistry Astronomy Astronomy Geology/Ecology Geology/Ecology Biology Biology