Electron Configurations

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Electron Configurations

• How does the Bohr Model of an atom compare to the
  Quantum Mechanical Model of an atom?

2
What is the wave nature of light?

• Visible light is part of electromagnetic
  radiation, a form of wave energy that travels
  through empty space in the form of alternating
  electric and magnetic fields.
• All waves consist of crest and troughs traveling
  away from a source at a velocity determined by
  the nature of the wave the material through
  which the wave passes.

3
How are frequency wavelength related?

• Frequency rate of wave vibration is the of
  waves that pass a given point per second.
• Expressed as Hz 1 Hz 1 wave/sec
• Wavelength determined by frequency velocity,
  it is the distance between points on a continuous
  wave.
• If frequency ? wavelength ?
• If frequency ? wavelength ?

4
Answer Questions

• Wave A Wave B
• What wave has the shortest wavelength?
• Which wave has the longest wavelength?
• Which wave has the lowest frequency?
• Which wave has the highest frequency?
• Which wave do you think has the most energy?

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Answer Questions

• Wave A Wave B
• What wave has the shortest wavelength? A
• Which wave has the longest wavelength? B
• Which wave has the lowest frequency? B
• Which wave has the highest frequency? A
• Which wave do you think has the most energy? A

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• 6. Which electromagnetic radiation would cause
  the most damage, gamma-rays or radio waves? Why?

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The more light bends the shorter the wavelength.
R O Y G B I V

• Which color of light bends the most?
• Describe its wavelength and frequency.
• Which color of light has the lowest frequency?
• Which color has the longest wavelength?

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The more light bends the shorter the wavelength.
R O Y G B I V

• Which color of light bends the most? Purple
• Describe its wavelength and frequency. Short
  Wavelength High Frequency
• Which color of light has the lowest frequency?
  Red
• Which color has the longest wavelength? Red

9
Niels Bohr (1913)

• Bohr
• placed p no in the center or nucleus of an
  atom
• Placed e- in rings around the nucleus
• worked in Rutherfords Lab

Electron
Electron
Proton
e- gets excited
Ground state
e- relax
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Bohr

• A Quantum model of H based on its spectrum.
• Predicted correctly frequencies of the lines H
  atomic emission spectrum.
• Proposed H atom has certain allowable energy
  states
• Lowest level ground state
• Gain energy excited states
• H has many different excited states

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Emission Spectrum of H, He, Hg, U
Visible Spectrum ROY G BIV
Hydrogen has 4 colors Red Aqua Blue Violet
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Proposed

• Ground state is the 1st energy level atom
  doesnt radiate energy
• Add energy from an outside source e- moves to
  higher energy level (orbit) to excited states
• An atom emits a photon (color of light)
  corresponding to the difference between energy
  levels of two orbits.

Light (has certain wavelength frequency color)
13
Draw the Bohr model of the atom

• The number of protons and neutrons are listed in
  the center of the atom
• The number of electrons must be determined
• The electrons are placed in concentric rings
  around the nucleus
• 1 The first ring can only hold 2 electrons
• 2 The next ring can only hold 8 electrons
• 3 The next ring can only hold 8 electrons
• 4 The next ring can only hold 18 electrons
• 5 The next ring can only hold 18 electrons
• 6 The next ring can only hold 32 electrons
• 7 The next ring can only hold 32 electrons

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Bohr Model WS

• Fill in the information and place the correct
  amount of e-s in each ring
• Fill in the orbitals from the inside (ground
  State) out (excited states)

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Problem

• Failed to explain spectrum of other elements.
• Did not fully account for atoms behavior
• Research shows e- do not move in circular orbits
• Did lay groundwork for other models

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What is the quantum mechanical model for atoms?

• (1924 Louis de Broglie 1892-1987)
• Proposed a model to account for fixed energy
  levels of Bohrs Model
• Thought that light waves have both wave
  particle like behavior.
• If waves have particle like behavior could
  particles have wavelike behavior?

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Erwin Shrödinger

• Austrian physicist using complex equation,
  developed quantum mechanical model (electron
  cloud) of the atom
• Electrons treated as waves
• Electrons not in circular orbits
• Mathematically predicts probable location of an
  electron

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Quantum Mechanical Model

• e- are treated as waves
• limits e- to certain values
• doesnt describe e- path
• 3-dimensional design
• atomic orbital describes e- probable location

e- wiggle as the move around nucleus
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Werner Heisenberg (1901- 1976)

• Heisenberg Uncertainty Principle
• Impossible to make any measurement on an object
  without disturbing the object, even a little.
• States it is fundamentally impossible to know
  precisely both the velocity position of a
  particle _at_ the same time.

Where is the e-?
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Assign Principle Quantum s (n)

• (n) increases as orbitals become larger
• e- away from nucleus have increased energy
• n principle energy level ground state (PEL)
• Ex n 1 ground state
• H has a n 1-6

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PEL contains

• energy sublevels s,p,d,f according to the shapes
  of the atoms orbitals.
• s - spherical
• p - dumbbell shaped
• d - f have different shapes

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Energy Levels

• While Bohrs model of an atom is an easy
  representation it is not correct. Electrons
  exist in energy levels and must be assigned
  correctly to determine the valence electrons
• There are 4 orbitals each holding a different
  number of electrons
• s holds 2 electrons
• p holds 6 electrons
• d holds 10 electrons
• f holds 14 electrons

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To determine the electron configuration for any
atom simply look at the periodic table

• Columns Groups Family
• Groups 1 - 2 are s orbitals (He)
• Groups 13 18 are p orbitals
• Groups 3 12 are d orbitals
• Lanthanide and Actinide are f orbitals

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Periodic Table

• Color your periodic table indicating the s, p, d,
  f elements
• Pp. 161 in book
• s yellow
• p purple
• d blue
• f green

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Fill in WS

• Energy levels are numbered from 1 to 7 and are
  where electrons are located. Energy levels can
  only hold a certain of electrons. Electrons
  fill inner energy levels before they fill outer
  energy levels. Electrons in the outer most energy
  level determine the behavior of an element.
  Another name for these electrons would be valence
  electrons. Atoms with full outer shells are
  stable or inert. Generally, that means 8
  electrons and is called the octet rule. The
  exception to this rule is He which has only 2
  valence electrons.

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Sublevels

• Sublevels are areas within an energy level.
• They are designated by the letters s, p, d, f.
• s holds 2 electrons __
• p holds 6 electrons __ __ __
• d holds 10 electrons __ __ __ __ __
• f holds 14 electrons. __ __ __ __ __ __

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Sublevels per Energy Level

• n 1 1 sublevel 1s
• n 2 2 sublevels 2s 2p
• n 3 3 sublevels 3s 3p 3d
• n 4 4 sublevels 4s 4p 4d 4f
• n 5-7 are the same as the 4th energy level

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Electron Configuration

• A method of keeping track of how many electrons
  are located at each energy level and which
  sublevel they are in. The number represents the
  energy level. The letter represents the sublevel.
  The superscript represents how many electrons are
  located at a certain place.

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• The period (row number on PT) is important in
  determining the energy level
• To write an electron configuration you must write
  all the electrons in the atom
• Energy level?1s2 superscript (number of
  electrons)
• Sublevel

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Aufbau Diagram

• 1s
• 2s 2p
• 3s 3p 3d
• 4s 4p 4d 4f
• 5s 5p 5d 5f
• 6s 6p 6d
• 7s 7p

Energy pathway for electrons
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Aufbau Diagram

• 1s
• 2s 2p
• 3s 3p 3d
• 4s 4p 4d 4f
• 5s 5p 5d 5f
• 6s 6p 6d
• 7s 7p

Notice the pathway goes from 4s to 3d to 4p. This
is b/c the 4s electrons have more energy than the
3d, but less energy than the 4p electrons.
d suborbitals are in 1 energy level less than the
period (row) the element is in. f suborbitals
are in 2 energy levels less than the period (row)
the element is in.
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Electronic Configurations

• The arrangement of electrons in an atom is called
  the atoms configuration.
• Electrons will arrange themselves in a way that
  gives the atom the lowest possible energy.
• Energy level?1s2 superscript (number of
  electrons)
• Sublevel

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3 rules define how electrons are arranged

• The Aufbau principle states that electrons will
  occupy the lowest energy level available
• The Pauli exclusion principle Two e- within same
  orbit must have opposite spins
• Hunds rule single e- with the same spin must
  occupy each equal energy orbit before additional
  e- with opposite spins can occupy the same
  orbital

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Practice Electron Configurations

• Fill in arrows to represent electrons
• Follow Aufbau pathway when filling orbitals
• Transfer arrows to other WS and write electron
  configuration notation for each atom

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Identify each element
36
Identify each element
Fluorine
Phosphorus
37
Electron ConfigurationExamples

• H 1s1
• He 1s2
• Li 1s2 2s1
• Be 1s2 2s2
• B 1s2 2s2 2p1
• C 1s2 2s2 2p2
• N 1s2 2s2 2p3
• O 1s2 2s2 2p4
• F 1s2 2s2 2p5
• Ne 1s2 2s2 2p6

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Electron ConfigurationExamples

• Na 1s2 2s2 2p63s1
• Mg 1s2 2s2 2p63s2
• Al 1s2 2s2 2p63s23p1
• Si 1s2 2s2 2p63s23p2
• P 1s2 2s2 2p63s23p3
• S 1s2 2s2 2p63s23p4
• Cl 1s2 2s2 2p63s23p5
• Ar 1s2 2s2 2p63s23p6
• K 1s2 2s2 2p63s23p64s1
• Ca 1s2 2s2 2p63s23p64s2

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Electron ConfigurationExamples

• Sc 1s2 2s2 2p63s23p64s23d1
• Ti 1s2 2s2 2p63s23p64s23d2
• V 1s2 2s2 2p63s23p64s23d3
• Cr 1s2 2s2 2p63s23p64s23d4
• Mn 1s2 2s2 2p63s23p64s23d5
• Fe 1s2 2s2 2p63s23p64s23d6
• Co 1s2 2s2 2p63s23p64s23d7
• Ni 1s2 2s2 2p63s23p64s23d8
• Cu 1s2 2s2 2p63s23p64s23d9
• Zn 1s2 2s2 2p63s23p64s23d10

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Electron ConfigurationExamples

• Cs 1s2 2s2 2p63s23p64s23d104p6
• 5s24d105p66s1
• Hg 1s2 2s2 2p63s23p64s23d104p6
• 5s24d105p66s24f145d10

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Noble Gas (Short Hand) Notation of Electron
Configurations

• Find the noble gas in the row above the element
  you need to write the notation for and put in
  brackets __ .
• Ex Looking for S (sulfur) the noble gas
  would be Neon
• SNe

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Noble Gas (Short Hand) Notation of Electron
Configurations

• 2. Write the notation starting in the period
  (row) the element is in.
• SNe3s23p4
• Write noble gas notation using these
• elements
• Br, Ag, U, Xe

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What are Valence Electrons?

• e-s that determine chemical properties of an
  element
• These e- are in the outermost orbitals usually
  the highest principle energy level

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How are valence e- determined

• Find which group (column) element is in and that
  is how many valence electrons the element has.
• Works for groups
• 1-2 (He has only 2 ve-) 13-18

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How are valence e- determined from electron
configurations

• SNe 3s2 3p4 (6 e- in outermost level)
• CsXe 6s1 (1 e- in outermost level)

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What are Electron Dot or Lewis Structures?(1875-1
946)

• LiHe 1s1 Li 1 ve-
• NeHe 2s2 2p6 Ne 8 ve-

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What are Electron Dot or Lewis Structures?(1875-1
946)

• LiHe 1s1 Li 1 ve-
• NeHe 2s2 2p6 Ne 8 ve-