Chapter 9, Part 1: Inorganic Analysis

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Chapter 9, Part 1Inorganic Analysis
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The Concept of Atoms

• The smallest unit of an element that retains the
  microscopic properties of the element.
• It can exist alone or be combined.
• It may be in any physical state.
• An atom can be represented by a sphere or other
  geometric figure.

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Atomic Theory

• Democritus (400 BC) matter is made up of tiny
  indivisible particle called atoms
• Lavoisier (1785) Law of Conservation of Mass in
  chemical reactions matter is not created or
  destroyed.
• Proust (1797) Law of Constant Composition
  element ratios in a compound are constant no
  matter what source or method of preparation.

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Law of Conservation of Mass
216 g HgO ---gt 200g Hg 16 g O2
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Daltons Atomic Theory (1803)

• Matter is made up of indivisible particles
  (atoms)
• Atoms cannot be created or destroyed
• All atoms of an element are identical
• Atoms combine in simple, whole-number ratios

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Law of Conservation of Mass Using Daltons Atomic
Theory
20 g H2 160 g O2 ---gt 180 g H2O
10 H2 5 O2 ---gt 10 H2O
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The Nuclear Atom
nucleus
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Location of Subatomic Particles
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Atomic Symbols
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Isotopes

• Atoms with the same number of protons, but
  different numbers of neutrons.
• Example
• Isotopes of chlorine
• 35Cl 37Cl
• chlorine - 35 chlorine -
  37
• p 17, n 18 p 17, n 20

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Number of Electrons

• An atom is neutral and the net charge is zero
• Number of protons Number of electrons
• Atomic number Number of electrons
• If protons ? electrons then a right superscript
  shows the sign and magnitude of the charge

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Subatomic Particles in Ions

• 31 31 31
• P1 P P-1
• 15 15 15
• 15 p 15 p 15 p
• 16 n 16 n 16 n
• 14 e- 15 e- 16 e-
• Cation Atom Anion

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Learning Check

• Naturally occurring carbon consists of three
  isotopes, 12C, 13C, and 14C-4. State the number
  of protons, neutrons, and electrons in each of
  these carbon atoms or ions.
• 12C 13C 14C-4
• 6 6
  6
• p _______ _______ _______
• n _______ _______
  _______
• e _______ _______
  _______

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Atomic Mass on the Periodic Table

• 17
• Cl
• 35.453

Atomic Number
Symbol
Atomic Mass (not Mass )
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Atomic Mass

• Measured relative to 12C 12.000 amu 1.6606x10
  -24 gram
• Amu are scaled up to to the gram level using
  Avogadros Number, 6.022x1023
• Atomic mass is the weighted average mass of all
  the atomic masses of the isotopes of that atom.

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Example of an Average Atomic Mass

• Cl-35 is about 75.5 and Cl-37 about 24.5 of
  natural chlorine.
• 35 x 75.5 26.4
• 100
• 35.5
• 37 x 24.5 9.07
• 100

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Shells, Subshells and Orbitals

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Electromagnetic Radiation
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Electromagnetic Radiation

• Light is emitted from atoms as EM radiation.
• EM radiation is a moving energy wave with
  electrical and magnetic components at right
  angles to each other.
• An EM wave travels at 3x108 m/s and has a
  discrete energy (E), frequency (n) and wavelength
  (?) .
• E hn or E hc/ ? so as E increases n increases
  and lambda decreases.
• h 6.63x10-34 Js and c n x ?

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Emission Spectra
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Emission Spectra of Elements
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Emission Spectra

• When a high voltage is applied to a gaseous
  element or compound a specific color of light is
  observed.
• When the light is passed through a prism to
  separate the colors a series of colored lines is
  observed representing energy changes of electrons
  in the atoms.
• The fact that only specific colored lines
  different for each element are observed that this
  stronglt supports the quantitization of electron
  energy.

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Electron Levels (Shells)

• The electrons in an atom are organized into
  shells like layers of an onion
• The shells closest to the nucleus are at the
  lowest potential energy.
• Identified by numbers 1, 2, 3, .. the first
  shell (1) is lowest in energy and so on 1lt2lt3

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Quantum Theory

• Energy changes in atoms occur in discrete steps
  or jumps
• When energy is absorbed by an atom it goes from
  the ground state to an excited state.
• When the atom returns to the ground state the
  energy is emitted as a photon.
• The difference in energy between the ground and
  excited state determines the color or energy of
  light absorbed or emitted.

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Quantum Theory
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Quantum Theory
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Quantum Mechanics

• All moving objects create waves.
• Moving electrons create standing waves like the
  vibrations of a string.
• The standing waves from electrons create
  orbitals.
• The larger the wave and the more nodes a wave
  has, the higher the energy of the orbital it
  creates.
• The electron wave also creates a probability
  distribution where the electron must exist.

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Chapter 9, Part 1Inorganic Analysis
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Electron Orbitals
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Electron Orbitals

• Orbitals are organized into shells and subshells
• Shell numbers (n) indicate the overall size and
  energy of all orbitals in a subshell
• Shells are identified by the principle quantum
  number (n) 1, 2, 3, 4, etc.
• Subshells indicate the shape of the orbitals as
  indicated by letters s, p, d, f
• An s subshell has one orbital, a p has three, d
  has five and f has seven orbitals

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Relative Sizes of s orbitals

2s
3s
1s
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Electron Orbitals
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Electron Orbitals
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Relative Energy of Electron Subshells

• Energy
• Levels Subshells
• n4 4slt 4plt 4d (gt 5s) lt 4f
• n3 3slt 3plt 3d (gt 4s)
• n2 2slt 2p
• n1 1s

Increasing Energy
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Electron Configurations

• List of orbitals containing electrons written in
  order of increasing energy with superscripts to
  indicate the number of electrons
• Rules for creating electron configurations
• Electrons fill the lowest energy levels first
• Orbitals can hold no more than 2 electrons each
• Fill each orbital in a subshell with one electron
  before pairing
• The order of filling for subshells of atoms is
  1s22s22p63s23p64s23d104p65s24d105p66s24f145d10,
  etc.

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Electron Configurations
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Electron Configurations

• Method 1 (Subshell method)
• N 1s22s22p3
• Method 2 (Orbital box method)
• N
• 1s 2s 2p
• Method 3 (Noble Gas method)
• N He2s22p3

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Electron Configurations
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Electron Configurations
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Valence Electrons

• Elements in a group are isoelectronic
• N He2s22p3
• P Ne3s23p3
• As Ar4s23d104p3
• Electrons outside the noble gas inner core are
  valence electrons
• The number of valence electrons can be obtained
  from the second or only digit of the group number