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Transcript of Chapter 4 Arrangement of Electrons in Atoms. New Atomic Model Rutherford model incomplete Early...
Chapter 4Chapter 4
Arrangement of Electrons in Atoms
Arrangement of Electrons in Atoms
New Atomic ModelNew Atomic Model
Rutherford model incomplete Early twentieth century-new
atomic model emerged Scientists noticed a relationship
between electrons and light
Rutherford model incomplete Early twentieth century-new
atomic model emerged Scientists noticed a relationship
between electrons and light
Properties of LightProperties of Light
Light behaves as a wave and a particle Wave description
Visible light is a kind of electromagnetic radiation
All forms of ER move at a speed of 3.0 X 108 m/s (vacuum)
Light behaves as a wave and a particle Wave description
Visible light is a kind of electromagnetic radiation
All forms of ER move at a speed of 3.0 X 108 m/s (vacuum)
B. EM SpectrumB. EM Spectrum
LOW
ENERGY
HIGH
ENERGY
B. EM SpectrumB. EM Spectrum
LOW
ENERGY
HIGH
ENERGY
R O Y G. B I V
red orange yellow green blue indigo violet
WavesWaves
Wavelength (λ) is the distance between corresponding points on adjacent waves. Measured in distance (visible 400-700 nm)
Frequency (ν) is defined as the number of waves that pass a given point in a specific time, usually one second.
One wave per second or wave/second is called a Hertz (Hz)
Wavelength (λ) is the distance between corresponding points on adjacent waves. Measured in distance (visible 400-700 nm)
Frequency (ν) is defined as the number of waves that pass a given point in a specific time, usually one second.
One wave per second or wave/second is called a Hertz (Hz)
C=λν Frequency and wavelength are
inversely related The longer the wave the less go by
per second (if speed remains constant)
C=λν Frequency and wavelength are
inversely related The longer the wave the less go by
per second (if speed remains constant)
B. EM SpectrumB. EM Spectrum
GIVEN:
ν = ?
λ = 434 nm = 4.34 10-7 m
c = 3.00 108 m/s
WORK:ν = c λ
ν = 3.00 108 m/s 4.34 10-7 m
ν = 6.91 1014 Hz
EX: Find the frequency of a photon with a wavelength of 434 nm.
EX: Find the frequency of a photon with a wavelength of 434 nm.
The photoelectric effectThe photoelectric effect
Refers to the emission of electrons from a metal when light shines on the metal (see clip)
Max Planck was studying the emission of light by hot objects.
Theorized that the objects emit energy in small, specific packets called quanta.
Refers to the emission of electrons from a metal when light shines on the metal (see clip)
Max Planck was studying the emission of light by hot objects.
Theorized that the objects emit energy in small, specific packets called quanta.
Albert Einstein expanded on Planck’s theory
Proposed ER has a dual wave-particle nature
Exhibits wavelike properties and can be thought of as a stream of particles
Albert Einstein expanded on Planck’s theory
Proposed ER has a dual wave-particle nature
Exhibits wavelike properties and can be thought of as a stream of particles
Each particle of light carries a quantum of energy.
Einstein called them photons A photon is a particle of ER having
zero mass and carrying a quantum of energy.
Each particle of light carries a quantum of energy.
Einstein called them photons A photon is a particle of ER having
zero mass and carrying a quantum of energy.
Einstein explained photoelectric effect by stating ER is absorbed by matter in whole numbers of photons.
To shoot off an electron ER must have enough energy according to Planck’s equation.
E=hv
Einstein explained photoelectric effect by stating ER is absorbed by matter in whole numbers of photons.
To shoot off an electron ER must have enough energy according to Planck’s equation.
E=hv
Photoelectric effect
1414
Photoelectric effectPhotoelectric effect
Photoelectric effect proved light behaves like a particle
Proved light’s dual nature
Photoelectric effect proved light behaves like a particle
Proved light’s dual nature
14
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A quantum of energy is the minimum quantity of energy that can be lost or gained by an atom.
Planck proposed the following: E = hν Planck’s constant; h = 6.626 X 10-
34 J•s
A quantum of energy is the minimum quantity of energy that can be lost or gained by an atom.
Planck proposed the following: E = hν Planck’s constant; h = 6.626 X 10-
34 J•s
GIVEN:
E = ?ν = 4.57 1014 Hzh = 6.6262 10-34 J·s
WORK:
E = hν
E=(6.626210-34J·s)(4.571014 Hz)
E = 3.03 10-19 J
EX: Find the energy of a red photon with a frequency of 4.57 1014 Hz.
EX: Find the energy of a red photon with a frequency of 4.57 1014 Hz.
Hydrogen-Atom Line-Emission Spectrum
Hydrogen-Atom Line-Emission Spectrum
When an electrical current is passed through a gas at low pressure, the potential energy of some of the gas’s electrons increase.
The lowest energy state of an electron is called its ground state.
A state in which an electron has a higher potential energy that it has in its ground state is an excited state.
When an electrical current is passed through a gas at low pressure, the potential energy of some of the gas’s electrons increase.
The lowest energy state of an electron is called its ground state.
A state in which an electron has a higher potential energy that it has in its ground state is an excited state.
Current passed through hydrogen gas gives a characteristic pinkish glow.
When the light was placed in a prism, four characteristic colors emerged.
Called the Hydrogen-Atom Line Emission Spectrum
Current passed through hydrogen gas gives a characteristic pinkish glow.
When the light was placed in a prism, four characteristic colors emerged.
Called the Hydrogen-Atom Line Emission Spectrum
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Hydrogen emission spectra
Hydrogen emission spectra
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Puzzle of the Hydrogen Atom Spectrum
Puzzle of the Hydrogen Atom Spectrum
Niels Bohr theorized that electrons can circle the nucleus only in allowed paths called orbits.
Orbits can be compared to rungs on a ladder--> electrons can be in one orbit or another but not in between.
Niels Bohr theorized that electrons can circle the nucleus only in allowed paths called orbits.
Orbits can be compared to rungs on a ladder--> electrons can be in one orbit or another but not in between.
ExplanationExplanation
Electrons can move to a higher-energy orbit by gaining energy
This process is called absorption. When the electron falls back down
to a lower energy a photon of ER is emitted.
The process is called emission. The energy of each photon
corresponds to a specific frequency (E=hv)
Electrons can move to a higher-energy orbit by gaining energy
This process is called absorption. When the electron falls back down
to a lower energy a photon of ER is emitted.
The process is called emission. The energy of each photon
corresponds to a specific frequency (E=hv)
Explanation (cont’d)Explanation (cont’d)
Bohr related the possible energy-level changes to the lines in the hydrogen emission spectrum.
Energy-level changes are named after the scientists that discovered them
Bohr related the possible energy-level changes to the lines in the hydrogen emission spectrum.
Energy-level changes are named after the scientists that discovered them
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Lyman seriesLyman series
Electron falls to the first energy level
Emits Ultraviolet radiation
Electron falls to the first energy level
Emits Ultraviolet radiation
Balmer seriesBalmer series
Electron falls to the second energy level
Emits visible light Discovered first (1885)
Electron falls to the second energy level
Emits visible light Discovered first (1885)
Paschen seriesPaschen series
Electron falls to the third energy level
Emits infrared radiation
Electron falls to the third energy level
Emits infrared radiation
Bohr’s model worked well for Hydrogen.
Didn’t work for any other element. Why?
Bohr’s model worked well for Hydrogen.
Didn’t work for any other element. Why?
Flame testsFlame tests
Flame tests are also used as a qualitative test for elements
When metals are heated the electrons enter the excited state, drop down to the ground state, and emit ER
Flame tests are also used as a qualitative test for elements
When metals are heated the electrons enter the excited state, drop down to the ground state, and emit ER
Lithium salts (ionic) give a red color
Sodium salts give a yellow color
Potassium salts give a lilac (purple) color
Lithium salts (ionic) give a red color
Sodium salts give a yellow color
Potassium salts give a lilac (purple) color
Copper salts - green
Strontium - crimson red
Barium - yellowish-green
Copper salts - green
Strontium - crimson red
Barium - yellowish-green
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These are the chemicals that are used in fireworks to
give color.
Watch.
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Quantum Model of the Atom
Quantum Model of the Atom
Bohr’s model didn’t make sense to scientists.
Why can electron’s only exist in certain energy levels?
Scientists began to think of electrons as waves
Bohr’s model didn’t make sense to scientists.
Why can electron’s only exist in certain energy levels?
Scientists began to think of electrons as waves
Electrons as wavesElectrons as waves
Light can exist as a wave and a particle
Why can’t electrons? 1924 Louis de Broglie suggested
electrons do behave as waves They follow the E=hv equation Electrons also show diffraction
pattern and interference patterns
Light can exist as a wave and a particle
Why can’t electrons? 1924 Louis de Broglie suggested
electrons do behave as waves They follow the E=hv equation Electrons also show diffraction
pattern and interference patterns
Electrons as wavesElectrons as waves
Diffraction refers to the bending of a wave as it passes by the edge of an object or through a small opening.
Interference occurs when waves overlap. It results in a reduction of in energy in some areas.
Diffraction refers to the bending of a wave as it passes by the edge of an object or through a small opening.
Interference occurs when waves overlap. It results in a reduction of in energy in some areas.
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Heisenberg Uncertainty Principle
Heisenberg Uncertainty Principle
States that it is impossible to determine simultaneously both the position and velocity of an electron or any other particle.
Because photons have about the same energy as electron, any attempt to locate the electron with a photon knocks the electron off course.
States that it is impossible to determine simultaneously both the position and velocity of an electron or any other particle.
Because photons have about the same energy as electron, any attempt to locate the electron with a photon knocks the electron off course.
Schrodinger’s Wave Equation
Schrodinger’s Wave Equation
1926 Austrian physicist Erwin Scrödinger used Heisenberg’s principle to develop a mathematical equation to explain electron behavior.
1926 Austrian physicist Erwin Scrödinger used Heisenberg’s principle to develop a mathematical equation to explain electron behavior.
Quantum theoryQuantum theory
Heisenberg and Schrödinger’s work paved laid foundation for modern quantum theory.
Quantum theory describes mathematically the wave properties of electrons and other very small particles.
Heisenberg and Schrödinger’s work paved laid foundation for modern quantum theory.
Quantum theory describes mathematically the wave properties of electrons and other very small particles.
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Atomic Orbitals and Quantum NumbersAtomic Orbitals and Quantum Numbers
Scientists use Quantum numbers to specify the properties of atomic orbitals and the properties of electrons in orbitals.
The first three quantum numbers indicate the main energy level, the shape, and the orientation of an orbital.
The fourth, the spin quantum number, describes the state of the electron in the orbital.
Scientists use Quantum numbers to specify the properties of atomic orbitals and the properties of electrons in orbitals.
The first three quantum numbers indicate the main energy level, the shape, and the orientation of an orbital.
The fourth, the spin quantum number, describes the state of the electron in the orbital.
Principal quantum numberPrincipal quantum number
Symbolized by n Indicates the main energy level
occupied by the electron. Whole numbers The lower the n value the closer to
the nuclues Ex/ n=1 n=2 n=3
Symbolized by n Indicates the main energy level
occupied by the electron. Whole numbers The lower the n value the closer to
the nuclues Ex/ n=1 n=2 n=3
Angular Momentum Quantum Number
Angular Momentum Quantum Number
Symbolized by l Orbitals of different shapes exist-
known as sublevels The angular momentum quantum
number indicates the shape
Symbolized by l Orbitals of different shapes exist-
known as sublevels The angular momentum quantum
number indicates the shape
Angular Momentum Quantum Number
Angular Momentum Quantum Number
Indicates the shape 4 shapes --> s, p, d, f l = 0 indicates s shape l = 1 indicates p shape l = 2 indicates d shape l = 3 indicates?
Indicates the shape 4 shapes --> s, p, d, f l = 0 indicates s shape l = 1 indicates p shape l = 2 indicates d shape l = 3 indicates?
Angular Momentum Quantum Number
Angular Momentum Quantum Number
s shape is spherical, it is the only sublevel possible in the first energy level (n=1)
s shape is spherical, it is the only sublevel possible in the first energy level (n=1)
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Angular Momentum Quantum Number
Angular Momentum Quantum Number
p sublevel is in a “dumbbell” shape
Available in the 2nd energy level (n=2)
p sublevel is in a “dumbbell” shape
Available in the 2nd energy level (n=2)
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Angular Momentum Quantum Number
Angular Momentum Quantum Number
d orbital available in the 3rd energy level
Shape more complex
d orbital available in the 3rd energy level
Shape more complex
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Angular Momentum Quantum Number
Angular Momentum Quantum Number
f shape available in 4th energy level
f shape available in 4th energy level
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Magnetic Quantum Number
Magnetic Quantum Number
Atomic orbitals can have the same shape but different orientations around the nucleus.
Magnetic quantum number- symbolized by m, indicates the orientation of an orbital around the nucleus in the xyz axis.
Atomic orbitals can have the same shape but different orientations around the nucleus.
Magnetic quantum number- symbolized by m, indicates the orientation of an orbital around the nucleus in the xyz axis.
Magnetic Quantum Number
Magnetic Quantum Number
s orbitals are spherical it can only have one orientation
p orbitals can have three orientations along the xyz axis.
d orbitals can have five different orientations
f can have 7 different orientations
s orbitals are spherical it can only have one orientation
p orbitals can have three orientations along the xyz axis.
d orbitals can have five different orientations
f can have 7 different orientations
Magnetic Quantum Number
Magnetic Quantum Number
Different orientations can occur simultaneously
A single orbital can hold a maximum of two electrons
Different orientations can occur simultaneously
A single orbital can hold a maximum of two electrons
Shape # orbitals max electrons first found
Shape # orbitals max electrons first found
s 1 2 n=1
p 3 6 n=2
d 5 10 n=3
f 7 14 n=4
Spin Quantum NumberSpin Quantum Number
An electron in an orbital behaves like a planet spinning on an axis.
Can either spin one way or the other
Given two possible values (+1/2 or -1/2)
Symbolized by arrows or by ms
An electron in an orbital behaves like a planet spinning on an axis.
Can either spin one way or the other
Given two possible values (+1/2 or -1/2)
Symbolized by arrows or by ms
Spin Quantum NumberSpin Quantum Number
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Electron ConfigurationsElectron Configurations
The arrangement of an atom’s electrons is known as its electron configuration.
The arrangement of an atom’s electrons is known as its electron configuration.
Electron ConfigurationsElectron Configurations
Electrons are added one by one according to three rules: Aufbau principle Pauli Exclusion principle Hund’s Rule
Electrons are added one by one according to three rules: Aufbau principle Pauli Exclusion principle Hund’s Rule
Aufbau principleAufbau principle
An electron occupies the lowest energy orbital that can receive it.
1s fills first, it can hold 2 electrons 2s fills second, also holds 2 2p fills third, holds 6 3s 3p 4s ? 3d ?
An electron occupies the lowest energy orbital that can receive it.
1s fills first, it can hold 2 electrons 2s fills second, also holds 2 2p fills third, holds 6 3s 3p 4s ? 3d ?
Aufbau principleAufbau principle
Why does the 4s come before the 3d?
Why does the 4s come before the 3d?
Aufbau PrincipleAufbau Principle
The 4s energy level is lower than the 3d
Think of it as the 4s shape is closer than the 3d shape
There is a pattern
The 4s energy level is lower than the 3d
Think of it as the 4s shape is closer than the 3d shape
There is a pattern
Pauli Exclusion PrinciplePauli Exclusion Principle
Electrons occupying the same orbital must have opposite spin states
Electrons occupying the same orbital must have opposite spin states
Hund’s RuleHund’s Rule
Electrons in equal energy orbitals don’t pair up unless they have to
Electrons in equal energy orbitals don’t pair up unless they have to
Representing Electron Configurations
Representing Electron Configurations
Three ways to represent electron configurations Orbital Notation Electron Configuration Notation Noble Gas Notation
Three ways to represent electron configurations Orbital Notation Electron Configuration Notation Noble Gas Notation
Orbital NotationOrbital Notation
Electrons are symbolized by arrows
Orbitals are symbolized by __
Electrons are symbolized by arrows
Orbitals are symbolized by __
Name the element.
Electron Configuration Notation
Electron Configuration Notation
Number of electrons are shown by adding a superscript the the sublevel Ex/ Hydrogen has how many
electrons? 1s1
Ex 2/ Carbon’s electron configuration?
1s22s22p2
Number of electrons are shown by adding a superscript the the sublevel Ex/ Hydrogen has how many
electrons? 1s1
Ex 2/ Carbon’s electron configuration?
1s22s22p2
How to use periodic table for electron configurationsHow to use periodic table for electron configurations Find the element on the periodic
table Know how the sublevels apply to
the periodic table Write all sublevels you “pass”
going left to right
Find the element on the periodic table
Know how the sublevels apply to the periodic table
Write all sublevels you “pass” going left to right
s1
s2
d1 d10
p1
d5
p6
Noble gas notationNoble gas notation
Shortcut to writing electron configurations
Find the noble gas that comes before the element
Put that noble gas in brackets Start from there
Shortcut to writing electron configurations
Find the noble gas that comes before the element
Put that noble gas in brackets Start from there
Noble Gas ConfigurationNoble Gas Configuration
Example: Chlorine has 17 electrons 1s22s22p63s23p5
Find the noble gas before it, put it in brackets
[Ne]3s23p5
[Ne] replaces the 1s22s22p6
Example: Chlorine has 17 electrons 1s22s22p63s23p5
Find the noble gas before it, put it in brackets
[Ne]3s23p5
[Ne] replaces the 1s22s22p6
Noble Gas ConfigurationNoble Gas Configuration
Iodine has 53 electrons! Written as [Kr]4d105s25p5
Iodine has 53 electrons! Written as [Kr]4d105s25p5
ExceptionsExceptions
There are many exceptions to the electron configuration pattern
All are found in the transition metal region of the periodic table
Ex Chromium 24 electrons Should be [Ar]3d44s2
Actually [Ar]3d54s1
There are many exceptions to the electron configuration pattern
All are found in the transition metal region of the periodic table
Ex Chromium 24 electrons Should be [Ar]3d44s2
Actually [Ar]3d54s1
ExceptionsExceptions
All elements in Copper’s Family should end in d9s2
Actually end in d10s1
Copper is [Ar]3d104s1
All elements in Copper’s Family should end in d9s2
Actually end in d10s1
Copper is [Ar]3d104s1
Why?Why?
We don’t know Best explanation is two half filled
orbitals is more stable than one completely filled one
And one completely filled d orbital is more stable than a half filled s
We don’t know Best explanation is two half filled
orbitals is more stable than one completely filled one
And one completely filled d orbital is more stable than a half filled s