The Quantum Theory of the Atom

1
The Quantum Theory of the Atom
2
Bohr

• Bohr proposed that the hydrogen atom has only
  certain allowable energy states.
• Bohr suggested that the single electron in a
  hydrogen atom moves around the nucleus in only
  certain allowed circular orbits.

3
De Broglie

• DeBroglie stated that electrons had wave like
  characteristics
• Came up with the equation
• (?) wavelength, (m) mass of particle, (v)
  velocity, (h ) Plancks constant 6.626 x10-34

4
The Heisenberg Uncertainty Principle

• Heisenberg concluded that it is impossible to
  make any measurement on an object without
  disturbing the objectat least a little.
• The Heisenberg uncertainty principle states that
  it is fundamentally impossible to know precisely
  both the velocity and position of a particle at
  the same time.

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The Schrödinger wave equation

• Combined the ideas of Bohr DeBroglie
• The atomic model in which electrons are treated
  as waves and particles is called the wave
  mechanical model of the atom or, more commonly,
  the quantum mechanical model of the atom.

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Quantum Mechanical Model of the Atom

• Principle Energy Levels
• The major energy levels of an atom
• Each level is a certain distance from the nucleus
  
• Higher levels contain more electrons than the
  lower levels.

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Quantum Mechanical Model

• Energy Sublevels
• Are sections within the principle energy levels
• Are represented by letters s,p,d,f
• The principle energy level number indicates how
  many orbitals are in that level
• s 1, p 3, d 5, f 7
• Each orbital has different orientations
• Each orientation holds two electrons that spin in
  opposite directions

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Orbitals on the Table
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Electron Configurations Orbital Notations

• Both are the arrangement of electrons in an atom
• Orbital Notations use arrows to represent
  electrons
• Electron configurations look like this
• 1s2 2s2 2p6 3s3 3p6
• There are several rules to writing each of these!

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Aufbau Principle
Lowest Energy
Lowest energy

• Remember the chart
• Each electron must occupy the lowest energy level
  first

Highest Energy
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Pauli Exclusion Principle

• In order for 2 electrons to share an orbital,
  they must have opposite spins
• In chemistry we designate spins with arrows.
• Therefore, if 2 electrons enter an orbital, they
  must enter ??

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Hunds Rule

• A single electron with the same spin must occupy
  each equal energy orbital before additional
  electrons will pair up with opposite spins
• You must fill before you pair
• For example, say you have 3 orbitals (dont
  forget that each orbital can hold at most 2
  electrons)
• You want to add 3 electrons

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How would they enter?

• __ __ __
• ?? ?_ __ or
• ? ? ? .
• The answer is
• ? ? ? .

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Orbital Notation

• Before we begin writing arrow diagrams there are
  a few things you need to know
• s can hold a max of 2 electrons
• p can hold a max of 6 electrons
• d can hold a max of 10 electrons
• f can hold a max of 14 electrons

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Orbital Notation

• Also
• s has 1 orbital
• p has 3 orbitals
• d has 5 orbitals
• f has 7 orbitals
• What do you notice about the number of orbitals
  compared to the number of electrons?

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Orbital Notation

• Lastly, you need to know the sequence of
  orbitals. Aufbau diagram
• follow the arrows, 1s fills first, notice 4s will
  fill before 3d

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Examples Orbital Notation

• Look at the following web lesson
• http// www.lon-capa.org/mmp/period/electron.htm

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Orbital Notation

• Write the arrow diagram for sodium
• Arrows represent electrons, so before you can
  start, you need to find the number of electrons.
• How many electrons does sodium have?
• 11

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Orbital Notation

• You will keep going until you reach 11 electrons
• Where do you always start?
• 1s
• 1s ??
• Where to next?
• 2s
• 1s ??
• 2s ??

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Orbital Notation

• How many electrons have you used so far?
• 4 (only 7 more to go)
• Whats next?
• 2p
• 1s ??
• 2s ??
• 2p ?? ?? ??

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Orbital Notation

• Only one more left. Where does it go?
• 3s
• 1s ??
• 2s ??
• 2p ?? ?? ??
• 3s ?

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Orbital Notation

• Draw the arrow diagram for Br
• 1s ??
• 2s ??
• 2p ?? ?? ??
• 3s ?? 3p ?? ?? ??
• 4s ??
• 3d ?? ?? ?? ?? ??
• 4p ?? ?? ? ,

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Electron Configurations

• Writing electron configurations is just a shorter
  way to write an arrow diagram
• You start with 1s and continue the configuration
  until you get the correct number of electrons

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Electron Configurations

• Write the full electron configuration for K
• K (19)
• 1s22s22p63s23p64s1
• The number of electrons in each orbital are
  written as superscripts
• Remember s 2, p 6, d 10, f 14
• Just follow the chart

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Electron Configurations

• Write the full electron configuration for Kr
• Kr (36)
• 1s22s22p63s23p64s23d104p6
• Write the full electron configuration for P
• P (15)
• 1s22s22p63s23p3

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Noble Gas Configurations

• Noble Gas configuration is just a short hand way
  to write an electron configuration
• Steps
• Find the element
• Find the noble gas before that element (Group 8A)
  and place it in brackets
• Move one spot
• Start the configuration from there and keep going
  until you get to your element

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Reading the periodic table

• s block the first 2 columns of the periodic
  table (starts with 1s)
• p block Groups 3A-8A, six columns (starts with
  2p)
• d block the center portion of the periodic
  table consisting of 10 columns (starts with 3d)
• f block the two bottom rows of the periodic
  table consisting of 14 columns (starts with 4 f)

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Orbitals on the Table
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Noble Gas Configurations

• Write the noble gas configuration for Na
• Find the Noble Gas before Na
• Ne
• Move one spot and start the configuration from
  there
• Ne3s1

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Noble Gas Configurations

• Write the noble gas configuration for Br
• Ar4s23d104p5
• Write the noble gas configuration for Mn
• Ar4s23d5

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Final Entry Configuration

• Final entry configuration the last thing in an
  electron configuration
• Its like a road map to the element
• Can Identify the element

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Final Entry Configuration

• What is the final entry configuration for Si?
• Find Si
• What block are you in (s, p, d, f)?
• 3p
• How many spots are you into p?
• 2
• 3p2

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Final Entry Configuration

• What is the final entry configuration for Ag?
• 4d9
• What is the final entry configuration for Cl?
• 3p6
• What is the final entry configuration for Na?
• 3s1

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Final Entry Configuration

• What element has the final entry configuration of
  4p3?
• As
• What element has the final entry configuration of
  4d1?
• Y