Transcript The Wave Nature of Light

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The Wave Nature of Light
• Crest – the highest point on a wave.
• Trough – the lowest point on a wave.
• Amplitude – the distance from the top of the
crest to the low point of the trough.
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The Wave Nature of Light
• Wavelength – the shortest distance between
two troughs or two crests.
• Frequency – the number of times a wave
passes a point in one second.
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Atomic Structure: Basic Concepts
The Electromagnetic Spectrum
Electromagnetic radiation travels in the form of
waves that have both electrical and magnetic
properties.
These electromagnetic waves can travel through
empty space.
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Atomic Structure: Basic Concepts
The Electromagnetic Spectrum
Electromagnetic waves travel through space at the speed of light, 300 million m/s.
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Atomic Structure: Basic Concepts
The Electromagnetic Spectrum
Electromagnetic radiation includes radio waves, microwaves, heat, and visible light.
All of these forms of radiant energy are parts of a whole range of electromagnetic
radiation called the electromagnetic spectrum.
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Atomic Structure: Basic Concepts
The Electromagnetic Spectrum
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Energy in Light
• Matter can only lose energy in small, specific
amounts.
• A Quantum is the smallest amount of energy
that can be gained or lost by an atom.
• The amount energy in a wave is related to its
frequency.
• The higher the frequency the more energy the
wave contains.
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Light as a Particle
• Thinking of light as a wave could not explain how
solar panels work.
• Einstein proposed that light acted like a wave and a
particle.
• A photon is a particle of light that has no mass and
holds one quantum of energy.
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Atomic Structure: Basic Concepts
Electrons and Light
The colors of light released from excited atoms of an element is called the emission
spectrum.
Emission Spectrum
• Each element has a distinct emission spectrum.
• The emission spectrum can be used to identify
elements.
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Atomic Structure: Basic Concepts
Electrons in Motion
Bohr (1885-1962) proposed that electrons must have enough energy to keep them
in constant motion around the nucleus.
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Atomic Structure: Basic Concepts
Electrons in Motion
Bohr’s atom was called the
planetary model.
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Atomic Structure: Basic Concepts
Evidence for Energy Levels
Bohr thought electrons can move around the nucleus only at certain distances.
These regions of space in which electrons can move around the nucleus are called
energy levels.
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Atomic Structure: Basic Concepts
Evidence for Energy Levels
Electrons absorbed energy and moved to
higher levels.
When the electrons fell back to a lower
level they gave off that energy as light
waves.
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Atomic Structure: Basic Concepts
The Electron Cloud Model
Scientists today realize that energy levels are not neat.
Instead, they are spherical regions in which electrons are most likely to be found.
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Atomic Structure: Basic Concepts
The Electron Cloud Model
The space around the nucleus of an atom where the atom’s electrons are found is
called the electron cloud.
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Atomic Structure: Basic Concepts
The Electron Cloud Model
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Atomic Structure: Basic Concepts
Electrons in Energy Level
Each energy level can hold a limited number of electrons.
The lowest energy level is the smallest and the closest to the nucleus.
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Atomic Structure: Basic Concepts
Electrons in Energy Level
This first energy level holds a maximum of two electrons.
The second energy level is larger because it is farther away from the nucleus. It
holds a maximum of eight electrons.
The third energy level is larger still and holds a maximum of 18 electrons.
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Atomic Structure: Basic Concepts
Energy Levels
A hydrogen atom has only one electron. It’s in the first energy level.
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Atomic Structure: Basic Concepts
Electrons in Energy Level
The electrons in the outermost energy level are called valence electrons.
Valence electrons determine the chemical properties of the elements.
All atoms in Group 1, like hydrogen, have one valence electron. Likewise, atoms in
Group 2 have two valence electrons.
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Atomic Structure: Basic Concepts
Electrons in Energy Level
An oxygen atom has eight electrons. Two of these fill the first energy level, and the
remaining six are in the second energy level.
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Atomic Structure: Basic Concepts
Lewis Dot Diagrams
A Lewis dot diagram illustrates valence electrons as dots around the chemical
symbol of an element.
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Atomic Structure: Basic Concepts
Lewis Dot Diagrams
Each dot represents one valence electron.
The element’s symbol represents the rest of the atom.
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Atomic Structure: Additional Concepts
Energy Levels and Sublevels
Experiments suggest that sublevels exist within a given energy level.
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Atomic Structure: Additional Concepts
Energy Levels and Sublevels
The energy sublevels are designated as s, p, d, or f.
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Atomic Structure: Additional Concepts
Energy Levels and Sublevels
The first energy level has one sublevel. It’s called the 1s sublevel.
The second energy level has two sublevels, the 2s and 2p sublevels
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Atomic Structure: Additional Concepts
Energy Levels and Sublevels
The third energy level has three sublevels: the 3s, 3p, and 3d sublevels.
The fourth level has s, p, d, and f sublevels.
The energies of the “s” sublevel is the lowest, while the “f” sublevel has the highest
energy.
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Atomic Structure: Additional Concepts
Orbitals
Electrons are distributed into sublevels to create the most stable arrangement.
The most stable arrangement has the lowest energy possible.
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Atomic Structure: Additional Concepts
Electron Configurations
This most stable arrangement of electrons in sublevels and orbitals is called an
electron configuration.
Electrons fill orbitals and sublevels beginning with the innermost sublevels and
continuing to the outermost.
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Atomic Structure: Additional Concepts
Orbitals and the Periodic Table
The periodic table is divided into blocks that show the sublevels and orbitals
occupied by the electrons of the atoms.
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Atomic Structure: Additional Concepts
Orbitals and the Periodic Table
Groups 1 and 2 have valence electrons
in s orbitals.
Groups 13 to 18 have valence electrons
in p orbitals.
Orbitals and the Periodic Table
• The “s” orbitals can
hold up to 2 electrons.
• “P” orbital can hold 6
electrons.
• D orbital holds 10.
• F holds 14.
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Atomic Structure: Additional Concepts
Building Electron Configurations
Hydrogen has a single electron in the first energy level. Its electron configuration is
1s1.
1 refers to the energy level
“s” is the sublevel
The superscript tells the number of electrons in the sublevel.
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Atomic Structure: Additional Concepts
Building Electron Configurations
Helium’s electron configuration is 1s2.
When the first energy level is filled, additional electrons must go into the second
energy level.
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Atomic Structure: Additional Concepts
Building Electron Configurations
Lithium’s electron configuration is 1s22s1.
Beryllium has two electrons in the 2s orbital, so its electron configuration is 1s22s2 .
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Atomic Structure: Additional Concepts
Building Electron Configurations
Each successive element has one more electron in the 2p orbitals.
The electron configuration for carbon is 1s22s22p2.
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Atomic Structure: Additional Concepts
Building Electron Configurations
At element number 10, neon, the p sublevel is filled with six electrons.
Neon has eight valence electrons; two are in an s orbital and six are in p orbitals.
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Atomic Structure: Additional Concepts
Building Electron Configurations
Neon’s electron configuration can be abbreviated: [He]2s22p6.
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Atomic Structure: Additional Concepts
Building Electron Configurations
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Atomic Structure: Additional Concepts
Building Electron Configurations
Notice that elements in the same group have similar configurations.
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Atomic Structure: Additional Concepts
Noble Gases
All the noble gases have filled
energy levels and,
therefore, stable electron
configurations.
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Atomic Structure: Additional Concepts
Noble Gases
These stable electron
configurations explain the lack
of reactivity of the noble
gases.
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Atomic Structure: Additional Concepts
Transition Elements
These are transition elements. Now the 3d sublevel begins to fill, producing atoms
with the lowest possible energy.
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Atomic Structure: Additional Concepts
Inner Transition Elements
These two series are called inner transition elements.