Atomic Models

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Chapter 5
Atomic Models
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5.1 Models Help Us Visualize the Invisible
World of Atoms
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Physical Model
Replicates an object on a more convenient scale
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Conceptual Model
Describes the behavior of a system
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Some examples
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Animation
Shells.mov
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Of course, these are not what atoms look like.
Rather, they are visual depictions that help us
to understand atomic behavior.
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5.2 Light Is a Form of Energy
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Electromagnetic Waves

1. Reinforce themselves

2) Propagate outwards in all directions at 3.0
x 108 m/s
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Electromagnetic Waves
also known as
Electromagnetic Radiation
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Electromagnetic Radiation
A series of waves emitted by vibrating
electrical charges and composed of vibrating
electric and magnetic fields that regenerate one
another.
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4 x 10
Hz
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14
14
4 x 10
7 x 10
Hz
Hz
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16
10
Hz
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20
10
Hz
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10
Hz
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Electromagnetic Spectrum
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Energy
Electromagnetic Spectrum
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What is white light?
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Spectroscope
A device used to observe the color components of
any light source
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What is black?
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5.3 Atoms Can Be Identified by the Light They
Emit
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Atomic Spectrum
The pattern of light frequencies formed by a
glowing element.
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5.4 Niels Bohr Used the Quantum Hypothesis to
Explain Atomic Spectra
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Quantum hypothesis
Light consists of a stream of energy packets.
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Quantum hypothesis
Light consists of a stream of energy packets.
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Quantum hypothesis
Light consists of a stream of energy packets.
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Quantum hypothesis
Light consists of a stream of energy packets.
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Quantum hypothesis
Light consists of a stream of energy packets.
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Quantum hypothesis
Light consists of a stream of energy packets.
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Quantum hypothesis
Light consists of a stream of energy packets.
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One energy packet
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quantum
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photon
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Nucleus
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Electron
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Low potential energy
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High potential energy
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n 1
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n 2
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n 3
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n 4
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Principle Quantum Number
An integer that specifies a quantized energy
level.
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n 3
n 2
n 1
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n 3
n 2
n 1
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n 3
n 2
n 1
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n 3
n 2
n 1
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n 3
n 2
n 1
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n 3
n 2
n 1
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n 3
5 billion Hz
n 2
n 1
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n 3
n 2
n 1
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n 3
n 2
n 1
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n 3
n 2
n 1
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n 3
n 2
n 1
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n 3
n 2
n 1
90
n 3
n 2
n 1
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n 3
n 2
7 billion Hz
n 1
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n 3
n 2
n 1
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n 3
n 2
n 1
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n 3
n 2
n 1
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n 3
n 2
n 1
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n 3
n 2
n 1
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n 3
n 2
n 1
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n 3
n 2
12 billion Hz
n 1
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n 3
n 2
n 1
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n 3
5 billion Hz
n 2
7 billion Hz
n 1
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n 3
5 billion Hz
12 billion Hz
n 2
7 billion Hz
n 1
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12 billion Hz
7 billion Hz
5 billion Hz


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12 billion Hz
7 billion Hz
5 billion Hz


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12 billion Hz
7 billion Hz
5 billion Hz


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5.5 Electrons Exhibit Wave Properties
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Electron waves may be represented by
1) Probability clouds
2) Atomic orbitals
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Probability cloud
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Atomic orbital
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Atomic orbital
90
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Atomic orbital
A region of space in which an electron of a given
energy has a 90 chance of being located.
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Several atomic orbitals may be represented at
once
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The electron is confined to the atom...
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The electron is confined to the atom...
...its energy, therefore
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is restricted to values that form standing
waves.
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In other words
The energy levels of an electron in an atom are
quantized.
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5.6 Energy-Level Diagrams Describe How Orbitals
are Occupied
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Each orbital has a capacity for two electrons
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s orbital
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s orbital
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s orbital
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Energy-level diagram
A diagram showing the orbitals of an atom in
order of increasing potential energy.
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Rubidium, Rb
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Rubidium, Rb
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Li
Lithium
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Be
Beryllium
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B
Boron
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C
Carbon
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N
Nitrogen
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O
Oxygen
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F
Fluorine
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Ne
Neon
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Electron Configuration
The arrangement of electrons in the orbitals of
an atom
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Li
Lithium
2
1
1s 2s
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Be
Beryllium
2
2
1s 2s
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B
Boron
2
2
1
1s 2s 2p
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C
Carbon
2
2
2
1s 2s 2p
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N
Nitrogen
2
2
3
1s 2s 2p
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Li
Lithium
2
2
4
1s 2s 2p
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F
Fluorine
2
2
5
1s 2s 2p
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Ne
Neon
2
2
6
1s 2s 2p
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Titanium, Ti
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2
6
2
6
2
2
2
1s 2s 2p 3s 3p 4s 3d
Titanium, Ti
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Periodic Table
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Hydrogen, H
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Lithium, Li
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Sodium, Na
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Potassium, K
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5.7 Orbitals of Similar Energies Can Be Grouped
Into Shells
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Seventh row
Sixth row
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Fifth row
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Fourth row
Third row
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Second row
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First row
2
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Second row
8
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Second row orbitals
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Seven rows of orbitals
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Seven rows of orbitals
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Seven rows of orbitals
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Periodic Table
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Periodic Table
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Periodic Table
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Periodic Table
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5.8 The Periodic Table Helps Us Predict
Properties of Elements
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Periodic Trends
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Atomic size
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Ionization energy
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Density
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Electronegativity
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Inner-shell shielding
Effective nuclear charge
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Inner-shell shielding
The tendency of inner-shell electrons to
partially shield outer-shell electrons from the
nuclear charge.
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Effective nuclear charge
The nuclear charge experienced by outer-shell
electrons.
Z
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Helium
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First shell
Helium
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First shell
Second shell
Lithium
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Animation
Shielding.mov
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Chlorine
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Chlorine
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Chlorine
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-10
Chlorine
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-10
Z 7
Chlorine
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Chlorine
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Chlorine
17 Actual nuclear charge
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Chlorine
17 Actual nuclear charge
-10 Inner shell electrons
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Chlorine
17 Actual nuclear charge
-10 Inner shell electrons
7 Effective nuclear charge
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Potassium
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Potassium
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Potassium
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-18
Potassium
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-18
Z 1
Potassium
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Potassium
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Potassium
19 Actual nuclear charge
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Potassium
19 Actual nuclear charge
-18 Inner shell electrons
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Potassium
19 Actual nuclear charge
-18 Inner shell electrons
1 Effective nuclear charge
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Atomic size
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Group 1
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Group 1
Increasing atomic size
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Period 2
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Period 2
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Period 2
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Period 2
3
4
5
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Period 2
Z 1
3
4
5
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Period 2
Z 1
Z 2
3
4
5
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Period 2
Z 1
Z 2
Z 3
3
4
5
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Period 2
Z 1
Z 2
Z 3
3
4
5
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Period 2
Z 1
Z 2
Z 3
3
5
6
7
8
4
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Period 2
Z 1
Z 2
Z 3
Z 4
3
5
6
7
8
4
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Period 2
Z 1
Z 2
Z 3
Z 4
Z 5
3
5
6
7
8
4
225
Period 2
Z 1
Z 2
Z 3
Z 4
Z 5
Z 6
3
5
6
7
8
4
226
Period 2
Z 1
Z 2
Z 3
Z 4
Z 5
Z 6
3
5
6
7
8
9
10
4
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Period 2
Z 1
Z 2
Z 3
Z 4
Z 5
Z 6
Z 7
3
5
6
7
8
9
10
4
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Period 2
Z 1
Z 2
Z 3
Z 4
Z 5
Z 6
Z 7
Z 8
3
5
6
7
8
9
10
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Period 2
Z 1
Z 2
Z 3
Z 4
Z 5
Z 6
Z 7
Z 8
3
5
6
7
8
9
10
4
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Period 2
Z 1
Z 2
Z 3
Z 4
Z 5
Z 6
Z 7
Z 8
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3
5
6
7
8
9
10
Sodium
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Period 2
Z 1
Z 1
Z 2
Z 3
Z 4
Z 5
Z 6
Z 7
Z 8
11
3
5
6
7
8
9
10
Sodium
4
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Period 2
Z 1
Z 2
Z 3
Z 4
Z 5
Z 6
Z 7
Z 8
Z 1
3
5
6
7
8
9
10
11
Sodium
4
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Period 2
Z 1
Z 2
Z 3
Z 4
Z 5
Z 6
Z 7
Z 8
Z 1
3
5
6
7
8
9
10
11
Sodium
4
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Period 2
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Period 2
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Period 2
Decreasing atomic size
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Atomic size
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7th shell
6th shell
5th shell
4th shell
3rd shell
2nd shell
1st shell
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7th shell
6th shell
5th shell
4th shell
3rd shell
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7th shell
6th shell
5th shell
4th shell
3rd shell
subshells
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Atomic size
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Ionization Energy
The amount of energy required to pull an electron
away from an atom
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Ionization energy
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Lithium
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Z 1
Lithium
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Z 1
Lithium
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Z 1
Lithium
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Z 1
Small distance, Stronger force
Lithium
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Cesium
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Z 1
Cesium
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Z 1
Cesium
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Z 1
Cesium
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Z 1
Greater distance, weaker force
Cesium
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Ionization energy
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Period 2
Z 1
Z 3
Z 5
Z 7
Z 2
Z 4
Z 6
Z 8
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Period 2
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Period 2
Z 1
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Period 2
Z 1
Z 7