Modern Atomic TheoryModern Atomic Theory

CP Chemistry ~ Unit 4CP Chemistry ~ Unit 4

Chapter 11 (p. 323)Chapter 11 (p. 323)

CP Chemistry Unit 7CP Chemistry Unit 7

3.1.10 B Describe concepts of models as a way 3.1.10 B Describe concepts of models as a way to predict and understand science and to predict and understand science and technology.technology.

3.1.10 C Apply patterns as repeated processes 3.1.10 C Apply patterns as repeated processes or recurring elements in science and technology.or recurring elements in science and technology.

3.4.10 A Explain concepts about the structure 3.4.10 A Explain concepts about the structure and properties of matter.and properties of matter.

3.4.10 B Analyze energy sources and transfers 3.4.10 B Analyze energy sources and transfers of heat.of heat.

DirectoryDirectory

I.] Atomic Models, Energy, & Light (EMR) I.] Atomic Models, Energy, & Light (EMR) – Atomic Models … History– Energy, Waves, & Light

II.]II.]Excited Atoms, Hydrogen, & Bohr

III.] III.] Wave-Mechanical Model Model

Atomic Models … HistoryAtomic Models … History

Match each name below Match each name below with the correct term(s) with the correct term(s) on the right!on the right!

Greeks (400 BC) (400 BC)Boyle (1627-1691)Boyle (1627-1691)Dalton (1766-1844) (1766-1844)JJ Thomson (1890’s)(1890’s)Lord Kelvin (1824-1907)(1824-1907)Rutherford (1910) (1910)Chadwick (1932) (1932)

Plum Pudding modelPlum Pudding model““atomos”atomos”NeutronNeutronGold Foil ExperimentGold Foil ExperimentIndivisible spheresIndivisible spheresCRTCRTElements can’t be broken Elements can’t be broken downdownProtonProtonElectronElectronNuclear atomNuclear atom

Ia.] History of Atomic TheoryIa.] History of Atomic Theory

Unanswered questions abound …Unanswered questions abound …

1.1. What are the electrons doing?What are the electrons doing?

2.2. What keeps the electrons from being drawn What keeps the electrons from being drawn into the nucleus?into the nucleus?

Ia.] History of Atomic TheoryIa.] History of Atomic Theory

Greeks … smallest particle of matter is Greeks … smallest particle of matter is “atomos”“atomos”

Ia.] History of Atomic TheoryIa.] History of Atomic Theory

John Dalton (1766 – 1844)John Dalton (1766 – 1844)Elements are made of tiny particles called Elements are made of tiny particles called

atomsatomsAll atoms of an element are identicalAll atoms of an element are identicalAtoms of an element are different from those of Atoms of an element are different from those of

other elementsother elementsAtoms combine with other atoms to form Atoms combine with other atoms to form

compoundscompoundsAtoms are indivisible, neither created nor Atoms are indivisible, neither created nor

destroyeddestroyed

Ia.] History of Atomic TheoryIa.] History of Atomic Theory

JJ Thomson (1856 – 1940)JJ Thomson (1856 – 1940)– Discovered electrons (CRT)Discovered electrons (CRT)– Electrons have a negative chargeElectrons have a negative charge

Ia.] History of Atomic TheoryIa.] History of Atomic Theory

Lord Kelvin (William Thomson) (1824-1907)Lord Kelvin (William Thomson) (1824-1907)– ““Plum Pudding” model of an atom (positive Plum Pudding” model of an atom (positive

cloud, pudding, with negative electrons, cloud, pudding, with negative electrons, plums, in it.plums, in it.

Ia.] History of Atomic TheoryIa.] History of Atomic Theory

5.5. Ernest Rutherford (1871-1937)Ernest Rutherford (1871-1937)– Gold Foil Experiment … used alpha particlesGold Foil Experiment … used alpha particles

““Like shooting a gun at a piece of paper and Like shooting a gun at a piece of paper and having the bullet bounce back”having the bullet bounce back”

– ““Nuclear atom” … atom with a nucleusNuclear atom” … atom with a nucleus– Nucleus … small, dense, and positiveNucleus … small, dense, and positive– Found protons (1919) in nucleus, positiveFound protons (1919) in nucleus, positive

Ia.] History of Atomic TheoryIa.] History of Atomic Theory

6.6. James Chadwick (1891-1971)James Chadwick (1891-1971)– Discovers the neutron, mass approximately Discovers the neutron, mass approximately

equal to the proton, no charge (neutral)equal to the proton, no charge (neutral)

7.7. 1920’s atom …1920’s atom …– Nucleus with protons and neutronsNucleus with protons and neutrons– Electrons outside of nucleusElectrons outside of nucleus

Ib.] Energy, Waves, & LightIb.] Energy, Waves, & Light

Characteristics of Waves …Characteristics of Waves …

Wavelength (Wavelength (λλ))Speed (c)Speed (c) CrestCrest

Frequency (Frequency (νν)) AmplitudeAmplitude TroughTrough

Ib.] Energy, Waves, & LightIb.] Energy, Waves, & Light

Types of waves …Types of waves …– Transverse … displacement is perpendicular Transverse … displacement is perpendicular

to the direction of propagationto the direction of propagation

– Longitudinal … displacement is parallel to the Longitudinal … displacement is parallel to the direction of propagationdirection of propagation

Ib.] Energy, Waves, & LightIb.] Energy, Waves, & Light

Properties wave demonstrate …Properties wave demonstrate …

– ReflectionReflection– RefractionRefraction– InterferenceInterference– DiffractionDiffraction

Ib.] Energy, Waves, & LightIb.] Energy, Waves, & Light

What do the following have in common?What do the following have in common?– MicrowavesMicrowaves– X-RaysX-Rays– ROY G BIVROY G BIV– Radio / TV wavesRadio / TV waves– Tanning bedsTanning beds– Cell phonesCell phones

Ib.] Energy, Waves, & LightIb.] Energy, Waves, & Light

Definition: EMR (electromagnetic radiation) Definition: EMR (electromagnetic radiation) radiant energy that exhibits wave-like radiant energy that exhibits wave-like behavior and travels through space at behavior and travels through space at the speed of light in a vacuum.the speed of light in a vacuum.

Composition: Composition:

- Electric component- Electric component

- Magnetic component- Magnetic component

Ib.] Energy, Waves, & LightIb.] Energy, Waves, & Light

Formula …Formula …

C = f (C = f (λλ))

E = hf (energy and frequency are directly E = hf (energy and frequency are directly proportionalproportional

E = hc / E = hc / λλ (energy and wavelength are inversely (energy and wavelength are inversely proportionalproportional

Ib.] Energy, Waves, & LightIb.] Energy, Waves, & Light

EM SpectrumEM Spectrum

Ib.] Energy, Waves, & LightIb.] Energy, Waves, & Light

What is light?What is light?

Answer …Answer …

a wave and a particle (photon)a wave and a particle (photon)

(wave – particle duality)(wave – particle duality)

Important: Important:

1.1. Different color = different wavelengthDifferent color = different wavelength

2.2. Different wavelength = different energyDifferent wavelength = different energy

Ib.] Energy, Waves, & LightIb.] Energy, Waves, & Light

So …So …

If we study the If we study the

electromagnetic spectra electromagnetic spectra

of elements we will get of elements we will get

clues into atomic clues into atomic

structure!structure!Flame Test: Strontium

II.] Excited Atoms, Hydrogen & II.] Excited Atoms, Hydrogen & Bohr Bohr When atoms are heated When atoms are heated

……

1.1. They absorb energy => They absorb energy => electrons jump to a electrons jump to a higher energy “excited higher energy “excited state” (unstable)state” (unstable)

2.2. When excited electrons When excited electrons fall back to lower levels, fall back to lower levels, they release energy they release energy (visible light).(visible light).

II.] Excited Atoms, Hydrogen & II.] Excited Atoms, Hydrogen & BohrBohrThe energy released The energy released

corresponds to the corresponds to the available energy available energy levels in that atom.levels in that atom.

Only certain energies Only certain energies are released are released (quantized energy).(quantized energy).

II.] Excited Atoms, Hydrogen & II.] Excited Atoms, Hydrogen & BohrBohr

If you look at a flame test through a If you look at a flame test through a spectroscope, what you see are lines of spectroscope, what you see are lines of color that correspond to the energy states color that correspond to the energy states of that atom!of that atom!

II.] Excited Atoms, Hydrogen & II.] Excited Atoms, Hydrogen & BohrBohr

Short Response …Short Response …

What is the significance of the observed What is the significance of the observed lines in the spectroscope when viewing an lines in the spectroscope when viewing an “excited” atom?“excited” atom?

II.] Excited Atoms, Hydrogen & II.] Excited Atoms, Hydrogen & BohrBohr

Niels Bohr (1885 – Niels Bohr (1885 – 1962)1962)– Solar system model of Solar system model of

the atomthe atom– Circular orbits of Circular orbits of

electrons correspond electrons correspond to energy levelsto energy levels

– Helpful model … Helpful model … unable to explain unable to explain atoms other than atoms other than hydrogenhydrogen

III.] Wave Mechanical Model (11.6)III.] Wave Mechanical Model (11.6)

Also known as the Quantum Mechanical Also known as the Quantum Mechanical Model (energy is “quantized;” a quantity)Model (energy is “quantized;” a quantity)

Proposed by Louis Victor de Broglie Proposed by Louis Victor de Broglie (1892-1987) and Erwin Schr(1892-1987) and Erwin Schröödinger dinger (1887-1961)(1887-1961)

Schrödinger’s Equation Schrödinger’s Equation

III.] Wave Mechanical Model (11.6)III.] Wave Mechanical Model (11.6)

Mechanics is a study of forces and Mechanics is a study of forces and motionsmotions– Newtonian Mechanics … describes the Newtonian Mechanics … describes the

behavior of visible objects traveling at behavior of visible objects traveling at ordinary velocities.ordinary velocities.

– Quantum Mechanics … describes the Quantum Mechanics … describes the behavior of extremely small particles at near behavior of extremely small particles at near light velocities.light velocities.

III.] Wave Mechanical Model (11.6)III.] Wave Mechanical Model (11.6)

Goal of mechanics related to atomic Goal of mechanics related to atomic structure … to describe the allowed structure … to describe the allowed electron energy states.electron energy states.Result … Quantum numbers (letters) tell Result … Quantum numbers (letters) tell us four things about the electron …us four things about the electron …– The distance of the electron from the nucleusThe distance of the electron from the nucleus– The shape of the electron cloud (probability)The shape of the electron cloud (probability)– The position of the electron in spaceThe position of the electron in space– The spin direction of the electronThe spin direction of the electron

III.] Wave Mechanical Model (11.6)III.] Wave Mechanical Model (11.6)

1.1. Electrons occupy orbitals (probability Electrons occupy orbitals (probability based) based) not not orbits!orbits!

Is the solar system model incorrect?Is the solar system model incorrect?

YES!YES!

2. Orbitals give no information about …2. Orbitals give no information about …– When an electron will be at a given point.When an electron will be at a given point.– The path of an electron.The path of an electron.

III.] Wave Mechanical Model (11.6)III.] Wave Mechanical Model (11.6)

This diagram is a This diagram is a representation of a representation of a mathematical or mathematical or probability model of probability model of an electrons location an electrons location around a nucleus.around a nucleus.

What does this model imply?

What doesn’t it imply?

III.] Atomic Orbital Structures (11.7)III.] Atomic Orbital Structures (11.7)

A.A. Principal Energy Levels (n = 1,2,3, …)Principal Energy Levels (n = 1,2,3, …)As level increases so does the energy.As level increases so does the energy.

(Roughly correspond to solar system rings.) (Roughly correspond to solar system rings.)

III.] Atomic Orbital Structures (11.7)III.] Atomic Orbital Structures (11.7)

B.B. Sublevels … each Principal Energy level is Sublevels … each Principal Energy level is divided into 1 or more sublevels.divided into 1 or more sublevels.

Example: Example:

Level 1 … 1 sublevel “s” (“s” = sharp)Level 1 … 1 sublevel “s” (“s” = sharp)

Level 2 … 2 sublevels s and “p” (“p” = principal)Level 2 … 2 sublevels s and “p” (“p” = principal)

Level 3 … 3 sublevels s, p, and “d” (“d” = diffuse)Level 3 … 3 sublevels s, p, and “d” (“d” = diffuse)

Level 4 … 4 sublevels s, p, d, and “f” (“f” = fundamental)Level 4 … 4 sublevels s, p, d, and “f” (“f” = fundamental)

III.] Atomic Orbital Structures (11.7)III.] Atomic Orbital Structures (11.7)

C.C. Orbitals … each Orbitals … each sublevel contains sublevel contains one or more one or more orbitals. Each orbitals. Each orbital is a orbital is a probability area for probability area for electrons.electrons.

All “s” sublevels All “s” sublevels contain 1 orbital contain 1 orbital which is sphericalwhich is spherical

III.] Atomic Orbital Structures (11.7)III.] Atomic Orbital Structures (11.7)

All “p” sublevels contain 3 orbitals All “p” sublevels contain 3 orbitals

that are each dumbbell shaped.that are each dumbbell shaped.

III.] Atomic Orbital Structures (11.7)III.] Atomic Orbital Structures (11.7)

All “d” sublevels contain 5 orbitals that can only described as different.

All “f” sublevels contain 7 orbitals.

III.] Atomic Orbital Structures (11.7)III.] Atomic Orbital Structures (11.7)

Pause …Pause …

Atoms contain _______________Atoms contain _______________

Levels contain _______________Levels contain _______________

Sublevels contain ____________Sublevels contain ____________

Orbitals contain ___________ Orbitals contain ___________

These electrons have opposite “spins,” These electrons have opposite “spins,” (designation … + or -, clockwise or (designation … + or -, clockwise or counterclockwise, up or down arrows)counterclockwise, up or down arrows)

III.] Atomic Orbital Structures (11.7)III.] Atomic Orbital Structures (11.7)

Levels …Levels …Sublevels …Sublevels …

Orbitals …Orbitals …Electrons … “spin”Electrons … “spin”

Pauli Exclusion Principal – “an atomic Pauli Exclusion Principal – “an atomic orbital can hold a maximum of two orbital can hold a maximum of two electrons and those electrons have electrons and those electrons have opposite spins.”opposite spins.”

IV.] Wave Mechanical Model (11.6)IV.] Wave Mechanical Model (11.6)

Principle Quantum Number … Principle Quantum Number … LEVELLEVEL– Corresponds to electron rings, shells, or orbits Corresponds to electron rings, shells, or orbits

in the Bohr modelin the Bohr model– Represented by the letter Represented by the letter nn– Primarily determines the electrons energy Primarily determines the electrons energy

(near nucleus = low energy)(near nucleus = low energy)– Always an integer greater than zero (n = 1, 2, Always an integer greater than zero (n = 1, 2,

3, …)3, …)– Within each Within each levellevel, the number of electrons = , the number of electrons =

2n2n22

IV.] Wave Mechanical Model (11.6)IV.] Wave Mechanical Model (11.6)

Angular Momentum Quantum Number … Angular Momentum Quantum Number … SUBLEVELSUBLEVEL– Represented by the letter Represented by the letter ll– Each level has a number of sublevels equal to Each level has a number of sublevels equal to

nn– The values for The values for ll= 0, 1, 2, 3, … n-1= 0, 1, 2, 3, … n-1– Within each level, the sublevels are named s, Within each level, the sublevels are named s,

p, d, f (sharp, principle, diffuse, fundamental) p, d, f (sharp, principle, diffuse, fundamental) – Increasing Increasing ll only slightly increases the only slightly increases the

electrons energyelectrons energy

Worksheet DiagramWorksheet Diagram

n

l

m

s

IV.] Wave Mechanical Model (11.6)IV.] Wave Mechanical Model (11.6)

Angular Momentum Quantum Number … Angular Momentum Quantum Number … ll– n = 1 … l = 0 (s) sphericaln = 1 … l = 0 (s) spherical– n = 2 … l = 0 & 1 (p) dumbbell shapen = 2 … l = 0 & 1 (p) dumbbell shape– n = 3 … l = 0, 1, & 2 (d) dumbbell w/ donut n = 3 … l = 0, 1, & 2 (d) dumbbell w/ donut – n = 4 … l = 0, 1, 2, & 3 (f) funny shapen = 4 … l = 0, 1, 2, & 3 (f) funny shape

IV.] Wave Mechanical Model (11.6)IV.] Wave Mechanical Model (11.6)

Magnetic Orbital Quantum Number … Magnetic Orbital Quantum Number … ORBITALORBITAL– Represented by the letter Represented by the letter mm– Electrons will pair up, the space that a pair of Electrons will pair up, the space that a pair of

electrons occupies is an orbitalelectrons occupies is an orbital– mm is always an integer; such that m = -l … 0 is always an integer; such that m = -l … 0

… +l… +l– Orbital has little effect on energyOrbital has little effect on energy

Worksheet DiagramWorksheet Diagram

n

l

m

s

IV.] Wave Mechanical Model (11.6)IV.] Wave Mechanical Model (11.6)

Number of OrbitalsNumber of Orbitals– Sublevel 0 (s) has one orbital … [0]Sublevel 0 (s) has one orbital … [0]– Sublevel 1 (p) has three orbitals … Sublevel 1 (p) has three orbitals …

[-1 ] [0] [+1][-1 ] [0] [+1]– Sublevel 2 (d) has five orbitals … Sublevel 2 (d) has five orbitals …

[-2] [-1] [0] [+1] [+2][-2] [-1] [0] [+1] [+2]– Sublevel 3 (f) has seven orbitals … Sublevel 3 (f) has seven orbitals …

[-3] [-2] [-1] [0] [+1] [+2] [-3] [-2] [-1] [0] [+1] [+2] [+3][+3]

IV.] Wave Mechanical Model (11.6)IV.] Wave Mechanical Model (11.6)

Magnetic Spin Quantum Number … Magnetic Spin Quantum Number … SPINSPIN– There are only two possible values … +1/2 or There are only two possible values … +1/2 or

– ½ (think of these as clockwise and – ½ (think of these as clockwise and counterclockwise spins) (sometimes counterclockwise spins) (sometimes represented as up and down arrows)represented as up and down arrows)

IV.] Wave Mechanical Model (11.6)IV.] Wave Mechanical Model (11.6)

Quantum Rules …Quantum Rules …– Pauli Exclusion Principle: no two electrons Pauli Exclusion Principle: no two electrons

may have the same set of four quantum may have the same set of four quantum numbersnumbers

– Hund’s Rule: when filling orbitals of equal Hund’s Rule: when filling orbitals of equal energy, fill so that as many electrons as energy, fill so that as many electrons as possible remain unpairedpossible remain unpaired