Electron Configuration and Quantum Numbers

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Electron Configuration and Quantum Numbers

• Where are the electrons?
• i.e.
• How are the electrons arranged in the atom?

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State Standard

• SC3. Students will use the modern atomic theory
  to explain the characteristics of atoms.
• b. Use the orbital configuration of neutral atoms
  to explain its effect on the atoms chemical
  properties.

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What you need to know

• How do E, ?, and v relate
• E ? , v ?
• v ? , E?
• ? ? , v ?
• ? ?, v ?
• v ? , ? ?
• ? ? , E ?
• ? ?, E ?

• Which one is greater in E
• uv or vis
• IR or gamma
• IR or vis
• uv or IR
• Arrange by increasing wavalength
• uv, IR, VIS, radio, X-ray

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Remember 4 Fundamental Forces

• Nuclear Strong Force regulates changes in the
  nucleus
• Normal or Traditional chemistry occurs in the
  outermost part of the atom where the electrons
  are located
• Hence, it is the exchange and/or sharing of the
  electrons that result in chemical reactions
  taking place
• The KEY to understanding chemical processes is
  understanding the location and processes that
  cause the electrons to rearrange.

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Nature tends towards lower energy

• Any process that occurs in nature occurs as a
  result of energy exchange
• A process/reaction will not occur unless it is
  favored energetically for the overall process
• KEY the end result must be more stable than the
  starting point
• For Example
• Cars roll down hill
• Water moves down hill
• Things fall downnot up

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Atomic Structure

• Atoms behave the same way.
• The electrons in the atom interact with the
  nucleus to achieve the lowest energy situation
  possible in the atom.
• We call the lowest energy state for the electrons
  in an atom the ground state.
• Higher energy states (when electrons have moved
  up on the energy laddermoved positions in the
  atom) are called excited states .

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3 Rules of electron arrangement

• Electrons obey three rules when finding their
  proper position (lowest energy) in an atom
• The Aufbau Principle
• Pauli Exclusion Principle
• Hunds Rule

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The Aufbau Principle

• The Aufbau Principle state that electrons occupy
  the lowest energy orbitals first.
• Berry translation start at the bottom (of E
  diagram) and work your way up.

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Pauli Exclusion Principle

• An orbital can hold 0, 1, or 2 electrons max. No
  more than 2.
• We will use an Energy Level Diagram to determine
  electron configuration. In this diagram we will
  use an up arrow ( ) or a down arrow ( ) to
  indicate the spin of the electron. Spin is
  simply a means of differentiating between two
  electrons in the same orbital.

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Hunds Rule

• For degenerate (same energy) orbitals, one
  electron enters each orbital until all degenerate
  orbitals contain 1 electron with parallel spins
  (arrow pointing in same direction) before
  electrons are paired up in the orbitals.
• Berry translation each one gets one before you
  pair them up (for same E level)

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Arrow Diagram

• Draw arrow diagram on the board.

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Energy Level Diagram

• Develop from Arrow Diagram on board

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Writing electron configurations

• On board
• Examples
• C 1s22s22p2
• Te 1s22s22p63s23p64s23d104p65s24d105p4
• Mn 1s22s22p63s23p64s23d5

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Noble Gas Core Electron Configurations

• Place EC of PREVIOUS noble gas in parenthesis and
  complete rest of configuration based upon
  knowledge of Periodic Table construction
• On board

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Noble Gas Core Electron Configurations

• V 1s22s22p63s23p64s23d3
• Mn 1s22s22p63s23p64s23d5
• Co 1s22s22p63s23p64s23d7
• Can be written using noble gas core
  configuration
• V Ar 4s23d3
• Mn Ar 4s23d5
• Co Ar 4s23d7
• But wait a minute. How do you know where to
  start?

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Electron Configuration and the Structure of the
Periodic Table

• There are some very interesting patterns we can
  see using the Periodic Table when looking at
  electron configuration.

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Electron Configuration and the Structure of the
Periodic Table
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Quantum Numbers

• Developed as a shorthand to electron
  configuration
• Bohr Atom only had 1 QN (n) b/c only circular
  orbits
• There are 4 quantum numbers used to describe
  todays quantum mechanical model using the 4
  different concepts we have discussed with
  electron configuration
• Energy level n
• Sublevel (orbital) type l
• Which specific orbital m (ml)
• Electron spin s (ms)

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Principal Quantum Number (n)

• Tells us the relative energy level the electron
  is in.
• Speaks of relative distance from the nucleus.
• Posible value n 1, 2, 3, etc.

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Sublevel Quantum Number (l)

• Tells the type of orbital the electron is in.
• Possible values l 0, 1, 2, , (n-1)
• Meaning l 0 s-orbital
• l 1 p-orbital
• l 2 d-orbital
• l 3 f-orbital

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Orbital Quantum Number (m)

• Tells exactly which orbital electron is in the
  sublevel
• Possible values - l, , 0 , , l
• Draw out orbital spacings and label
• s-orbital ___
• 0
• p-orbital ___ ___ ___
• -1 0 1
• d-orbital ___ ___ ___ ___ ___
• -2 -1 0 1 2
• f-orbital ___ ___ ___ ___ ___ ___ ___
• -3 -2 -1 0 1 2 3

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Spin Quantum Number (s)

• Tells if spin up or down
• 1/2 -1/2

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Putting it all together

• Indicate the 4 quantum numbers of the electrons
  below
• n l m s
• 4s2 ___ 4 0 0 1/2
• 0
• 5d9 __ __ __ __ __ 5 2 1 -1/2
• -2 -1 0 1 2

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Valence Electrons

• Outermost electrons are the ones that get
  involved in the chemical bondingthose imbedded
  in the noble gas core rarely get involved
• Outermost s p electrons
• Always have the highest n in ec
• Easy to determine how many there are using PT
• Practice, Practice, Practice

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Ions

• Outermost electrons are the ones involved in
  chemical bonding
• Hence, the valence electrons are the ones that
  are gained/lost or exchanged in chemistry
• Hence, these are the ones that are adjusted FIRST
  in the ec of neutral atom

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Related Sites

• http//www.fordhamprep.org/gcurran/sho/sho/lessons
  /lesson36.htm
• http//wine1.sb.fsu.edu/chm1045/notes/Struct/EConf
  ig/Struct08.htm
• http//education.jlab.org/qa/electron_config.html
• http//www.chemicalelements.com/show/electronconfi
  g.html
• http//en.wikipedia.org/wiki/Electron_configuratio
  n

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