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Unit 7: Electrons
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Electromagnetic (EM) radiation
O A form of energy produced by electrical and magnetic vibrations, or by the movement of electrically charged particles
O Can travel in a “vacuum” (they do NOT need a medium)
O Travel at the speed of light
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Electromagnetic Spectrum
O Page 120
Frequency and energy have a direct relationship. Watch this.
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The Electromagnetic Spectrum
• Shows all types of EM radiation• Red Martians Invaded Venus Using X-Ray Guns• Shorter wavelength, high frequency light has
higher energy. Write this on your diagram– Radio wave has the lowest energy.– Gamma ray has the highest energy.
• High energy electromagnetic radiation damages biological molecules. It is called ionizing radiation
Visible lightOHas wave-like and particle-like
propertiesOA particle of light is called a photon.• Make the colors
of the rainbow• ROY. G. BIV• Each color has
a different wavelength, energy, and frequency
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Wave propertiesO (f) Frequency-number of waves
that pass a given point per unit of time. (Hz)
O () Wavelength- distance between similar points in a set of waves (crest to crest.) (m)
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Wave propertiesO Amplitude- distance from crest
or trough to the normal (baseline). Energy- Waves transmit energy. The amount of energy determines the amplitude and the frequency.
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Energy & AmplitudeO DIRECTLY related O Determines the intensity of lightO The bulb on the right is emitting
energy with a higher amplitude than the bulb on the left
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Amplitude and Wavelength
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Write this
Speed of the wave
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Write everything
Practice ProblemO What is the wavelength of a radio wave
with a frequency of 1.01 x 108 Hz? c = λ X f3.00 X 108 = λ X 1.01 x 108
λ = 3.00 X 108 1.01 x 108
λ = 2.97 m
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Energy of Electromagnetic Waves
O The energy is carried in small packages called photons. The energy carried in each photon is calculated by:
E = hfO E = energyO h = Planck’s constant =h = 6.63 x 10-34
JsO energy and frequency are DIRECTLY
related
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Write everything
Electrons and LightVocabulary:Ground State- the electron
occupies the LOWEST energy level.
Excited State- the electron temporarily occupies a HIGHER energy level.
Energy is needed to go up a level
Photons are released when falling down a level.
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Write everything
QuantumO The specific amount of
energy absorbed to excite an electron
O The specific amount of energy released when an electron falls to the ground state.
Energy in Energy out
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Atoms and Photons and ColorO Each atom’s electrons “jump” to certain
excited states. O Each “fall” releases a photon of a
certain wavelength. These wavelengths of light correspond to certain colors of light. The colors of light emitted by an atom’s electrons can be used to identify the element.
O The brightness of the color depends on the number of photons emitted.
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Where are the Electrons in the Cloud?
O Electrons are located at specific distances from the nucleus
O The distance from the nucleus determines the amount of energy associated with the electrons
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Principal Energy LevelsO 7 Energy Levels
O Abbreviated “n” O n= 1 is closest to
nucleus and has least energy
O n=7 is furthest from nucleus and has most energy
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Energy Levels
O Electrons are restricted to an energy level. O Electrons occupy the lowest energy level
possible because electrons are lazy!O On the periodic table, each period
(horizontal row) is an energy level
Energy levels contain sublevels
O There are four types of sublevelsO s, O p, O d, O f
Sublevels have different energies spdf: sublevel
energies in increasing orders is lowest energy p is next highest
d follows p in energy f is highest
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Energy Sublevels & the PT
Label your periodic tables according to the diagram
Orbital =The answer to a math problem.
O The math question?O Solve the above equation to tell us
where the electron is found in the atom.
O The answer tells you what level and sublevel the electron can probably be found.
Each sublevel has orbitals that contain
electrons
One orbital can contain 2 electrons. They must have opposite spin. Pauli Exclusion Principle
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O The maximum number of electrons that can occupy a specific energy level can be calculated
O Formula is 2n2 n = energy level
O Calculate electrons for the 3rd energy level:
O 2(3)2 = 18 electrons in the 3rd level
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Locating ElectronsO There are two ways to show where
the electrons are found in the atomO Orbital filling diagramsO Electron configurations
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Follow the rules when placing electrons
O Aufbau Principle- electrons go to the lowest energy level first.
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Follow the rules when placing electrons
O Hunds Rule- no orbital shares electrons until it has to share. Space them out to minimize repulsion of electrons.
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Locating Electrons
Orbital Filling Diagrams
O Use arrows to represent electrons in orbitals.
O The number of arrows must match the number of electrons contained in the atom
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PracticeO Hydrogen:O Oxygen:O Argon:O Copper:
1s1
1s1 2s2 2p4
1s2 2s2 2p6 3s2 3p6
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Electron ConfigurationO Shorthand method
for describing the arrangement of electrons
O Composed of the principal energy level followed by the energy sublevel and includes a superscript with the # of electrons in the orbitals of that sublevel
Electron ConfigurationO Electron Configuration is
ordered the way you read a book: from left to right and top to bottom
O Note that d orbital is 1 energy level behind and the f orbital is 2 energy levels behind the s & p orbitalsThe order: 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s2 5f14 6d10 7p6 etc.
Electron ConfigurationIA VIII
A
1 s IIA IIIAIV
AVA VI
AVII
As
2 s s p p p p p p
3 s s p p p p p p
4 s s d d d d d d d d d d p p p p p p
5 s s d d d d d d d d d d p p p p p p
6 s s f d d d d d d d d d p p p p p p
7 s s f d d
f f f f f f f f f f f f f d
f f f f f f f f f f f f f d 33
Orbital Filling Diagrams
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Electron Configuration
O Electron Configuration: 1s22s22p6
O Orbital Filling Diagram:
O Orbital image:
Noble Gas ConfigurationO Shorthand electron
configuration1. Give the symbol of the
noble gas in the previous energy level in brackets
2. Give the configuration for the remaining energy level
Example: Sulfur = 1s22s22p63s23p4
[Ne]3s23p4
Valence Electrons
O Valence electrons: found in the outermost energy levelO These electrons are used for
bondingO Example: Nitrogen = 1s2 2s2 2p3
O Add up the number of e- (superscripts) in the highest energy level
O Nitrogen has 2 + 3 = 5 valence electrons
O Core electrons: found in the inner
O energy levels. Nitrogen = 1s2 2s2 2p3
The number of valence electrons is equal to the number in the 1’s place of the group number
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Lewis-Dot DiagramsO Lewis Dot Diagrams are a way to
represent the valence electrons in an atom.O Element’s symbol represents the nucleus
and inner-level electronsO Dots represent the valence electronsO Dots are placed one at a time on the four
sides of the symbol, then paired until all valence electrons are used…
O Maximum of 8 e- will be around the symbol
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Lewis-Dot Diagrams
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Ions
O Ions are atoms that have gained or lost electrons; indicated by a superscript that shows the ion’s charge
O Cl 1s22s22p63s23p5
O Cl-1 1s22s22p63s23p6 chlorine added an electron
Chlorine adds a valence electron and
becomes a negative ion (anion).
O Sodium loses a valence electron and becomes a pawsitive ion (cation).
Can you tell which atoms are in ground state and which are
excited?1s2 2s2 2p6 3s2 4p1
1s2 2s2 2p6 3s2 3p6 3d6
1s2 2s2 2p3 4s1
1s2 2s2 2p6 3s2 3p6 3d8
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