Atomic Structure Electron Configuration

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Atomic StructureElectron Configuration
Scandium 3-D video (231)
3-D Graphic Examples of Atomic Orbitals
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Review
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Review
Jumping Electrons

• normally electrons exist in the ground state,
  meaning they are as close to the nucleus as
  possible
• when an electron is excited by adding energy to
  an atom, the electron will absorb energy and
  "jump" to a higher energy level
• heating a chemical with a
• Bunsen burner is enough
• energy to do this

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Review

• after a short time, this electron will
  spontaneously "fall" back to a lower energy
  level, giving off a quantum of light energy
  called a photon
• the key to Bohr's theory was the fact that the
  electron could only "jump" and "fall" to precise
  energy levels, thus emitting a limited spectrum
  of light.
• quantum is the amount of energy required to move
  an electron from one energy level to another

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Quantum Numbers (however, actual numbers are
often not used)

• each electron in an atom is described by four
  different quantum numbers
• think of the 4 quantum numbers as the address of
  an electron country gt state gt city gt street
• electrons fill low energy orbitals before they
  fill higher energy ones
• the first three of these quantum numbers (n, l,
  and m) represent the three dimensions in which an
  electron could be found
• the fourth quantum number (s) refers to a certain
  magnetic quality called spin

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Quick intro, more later.

• Principle quantum number (n)
• describes the SIZE of the orbital or ENERGY LEVEL
  (shell) of the atom.
• Angular quantum number (l)
• a SUB-LEVEL (shell) that describes the type or
  SHAPE of the orbital
• Magnetic quantum number (m)
• the NUMBER of orbitals
• describes an orbital's ORIENTATION in space
• Spin quantum number (s)
• describes the SPIN or direction (clockwise or
  counter-clockwise) in which an electron spins

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Principle Quantum (n) LEVEL/SIZE 1 2 3 4
Angular Quantum (l) ORBITAL SHAPE or SUBLEVEL s s p s p d s p d f
Magnetic Quantum (m) AXIS/ ORIENTATION or ORBITALS 1 1 orbital 1 3 4 total orbitals 1 3 5 9 total orbitals 1 3 5 7 16 total orbitals
Spin Quantum (s) DIRECTION OF ELECTRON SPIN 2 e- 8 e- 18 e- 32 e-
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4f 4d 4p 4s
14 (7)
10 (5)
6 (3)
level and sub-level max. of electrons
of electrons number of orbitals
2 (1)
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3d 3p 3s
10 (5)
6 (3)
2 (1)
18
2p 2s
6 (3)
2 (1)
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1s
2 (1)
2
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Principle Quantum Number (n) or Energy Level

• values 1-7 used to specify the level the electron
  is in
• describes how far away from the nucleus the
  electron level is
• the lower the number, the closer the level is to
  the atom's nucleus and less energy
• maximum of electrons that can fit in an energy
  level is given by formula 2n2

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Angular Quantum Number (l) or Sub-Levels

• determines the shape of the sub-level
• number of sub-levels equal the level number
• ex. the second level has two sub-levels
• they are numbered but are also given letters
  referring to the sub-level type
• l0 refers to the s sub-level
• l1 refers to the p sub-level
• l2 refers to the d sub-level
• l3 refers to the f sub-level

just know this
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Magnetic quantum number (m) or Orbitals

• Electron Orbitals YouTube 137
• the third of a set of quantum numbers
• tells us how many sub-levels there are of a
  particular type and their orientation in space of
  a particular sub-level
• only two electrons can fit in an orbital
• electron

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S sub-levelhas only 1 orbitalonly holds two
electrons
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P sub-levelhas 3 orbitalsholds up to six
electrons
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D sub-levelhas 5 orbitalsholds up to 10
electrons
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F sub-levelhas 7 orbitals holds up to 14
electrons
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Spin quantum number (s)

• the fourth of a set of quantum numbers
• number specifying the direction of the spin of an
  electron around its own axis.
• only two electrons of opposite spin may occupy an
  orbit
• the only possible values of a spin quantum number
  are 1/2 or -1/2.

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Principle Quantum (n) SHELL/SIZE 1 2 3 4
Angular Quantum (l) ORBITAL SHAPE or SUBSHELL s s p s p d s p d f
Magnetic Quantum (m) AXIS/ ORIENTATION or ORBITALS 1 1 orbital 1 3 4 total orbitals 1 3 5 9 total orbitals 1 3 5 7 16 total orbitals
Spin Quantum (s) DIRECTION OF ELECTRON SPIN 2 e- 8 e- 18 e- 32 e-
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Table 3-6b Orbitals and Electron Capacity of the First Four Principle Energy Levels Table 3-6b Orbitals and Electron Capacity of the First Four Principle Energy Levels Table 3-6b Orbitals and Electron Capacity of the First Four Principle Energy Levels Table 3-6b Orbitals and Electron Capacity of the First Four Principle Energy Levels Table 3-6b Orbitals and Electron Capacity of the First Four Principle Energy Levels
Principle energy level (n) Type of sublevel Number of orbitals per type Number of orbitals per level(n2) Maximum number of electrons (2n2)
1 s 1 1 2
2 s 1 4 8
2 p 3 4 8
3 s 1 9 18
3 p 3 9 18
3 d 5 9 18
4 s 1 16 32
4 p 3 16 32
4 d 5 16 32
4 f 7 16 32
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Rules for Writing Electron Configurations

• a method of writing where electrons are found in
  various orbitals around the nuclei of atoms.
• three rules in order to determine this
• Aufbau principle
• Pauli exclusion principle
• Hunds rule

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Aufbau Principle

• electrons occupy the orbitals of the lowest
  energy first
• each written represents an atomic orbital
  (such as or or or .)
• electrons in the same sublevel/shell have equal
  energy ( same energy as )
• principle energy levels/shells (1,2,3,4..) can
  overlap one another
• ex 4s orbital has less energy than a 3d orbital

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Pauli Exclusion Principle
Hamster video 100

• only two electrons in an orbital
• must have opposite spins
• represents one electron
• represents two electrons in an orbital

actually incorrect as well, see next slide
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Hunds Rules

• every orbital in a subshell must have one
  electron before any one orbital has two electrons
• all electrons in singly occupied orbitals have
  the same spin.

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Writing Orbital Diagrams
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Energy
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• Orbitals grouped in s, p, d, and f orbitals
  (sharp, proximal, diffuse, and fundamental)

s orbitals
d orbitals
p orbitals
f orbitals
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Boron Atomic 5
http//colossus.chem.umass.edu/genchem/whelan/clas
s_images/Orbital_Energies.jpg
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Boron ion (3) Atomic 5
http//colossus.chem.umass.edu/genchem/whelan/clas
s_images/Orbital_Energies.jpg
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Neon Atomic 10
http//colossus.chem.umass.edu/genchem/whelan/clas
s_images/Orbital_Energies.jpg
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Bromine Atomic 35
http//colossus.chem.umass.edu/genchem/whelan/clas
s_images/Orbital_Energies.jpg
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Bromine ion (1-) Atomic 35
http//colossus.chem.umass.edu/genchem/whelan/clas
s_images/Orbital_Energies.jpg
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?
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Orbital diagrams
Electron Configurations
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Writing Electron Configurations

• To write out the electron configuration of an
  atom
• use the principal quantum number/energy level
  (1,2,3, or 4)
• use the letter term for each sub-level (s,p,d, or
  f)
• dont worry about orientation such as x,y,z axis
  but you do have to be able to draw these for IB
• use a superscript number indicates how many
  electrons are present in each sub-level
• hydrogen 1s1.
• Lithium 1s22s1.
• dont write anything for spin

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Electron Configurations

• 2p4

Number of electrons in the sublevel
Energy Level
Sublevel
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2
4f14 etc.
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Order of Electrons
Sometimes levels are switched in order to keep
the level together. I hate when they do that! 4s
requires less energy and I think it should be
before 3d.

• 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2
  4f14 5d10 6p6 7s2 5f14 6d10 7p6

Weird electron configuration video (324)
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• exceptions (dont need to know this, just be
  aware that there are exceptions)
• orbitals like to be empty, half filled, or full
• therefore, an electron leaves the 4s (leaving it
  half full) and goes to the 3d in order to make it
  full

Cr we would predict 1s2 2s2 2p6 3s2 3p6 4s2 3d4 but it is actually 1s2 2s2 2p6 3s2 3p6 4s13d5
Cu we would predict 1s2 2s2 2p6 3s2 3p6 4s2 3d9 but it is actually 1s2 2s2 2p6 3s2 3p6  4s1 3d10
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Noble Gas Shortcut
same