Chapter 1' ATOMIC STRUCTURE AND THE PERIODIC TABLE

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PRINCIPALS OF CHEMISTRY I (CEM 141) Dr. BÙI
TH? B?U HUÊ College of Science Cantho University
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Chapter 1. MATTER AND MEASUREMENT Chapter 2.
ATOMS, MOLECULES AND IONS Chapter 3.
STOICHIOMETRIC Chapter 4. ATOMIC STRUCTURE AND
THE PERIODIC TABLE Chapter 5. CHEMICAL BONDS
AND MOLECULAR STRUCTURE Chapter 6. STATES
OF MATTER Chapter 7. ENERGY AND CHEMICAL
REACTIONS Chapter 8. SOLUTIONS Chapter 9.
CHEMICAL EQUILIBRIA
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References

• 1. Brady and Holum. 1996. Chemistry the Study
• of Matter and its Changes.
• 2th Ed., John Wiley Sons. Inc. New York.
• 2. Umland, Jean B., 1993. General Chemistry.
• West publishing company.
• 3. Zumdahl, Steven S. 1995. Chemical Principal.
• 2th Ed. DC. Health company. Toronto.
• 4. http//www.chemistry.msu.edu/Courses/
• 5. http//antoine.frostburg.edu
• 6. http//chemed.chem.purdue.edu
• 7. http//www.chem1.com/chemed/genchem.html
• http//www.cbu.edu/mcondren/lectures.htm
• http//ull.chemistry.uakron.edu/GenChem/index.htm
  l

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Chapter 4. ATOMIC STRUCTURE AND THE
PERIODIC TABLE

• Objectives
• Understand atomic structure of an atom
  including its mass number, isotopes and orbitals.
• Know how to account for the structure of the
  periodic table of the elements based on the
  modern theory of atomic structure.
• Understand general trends of several important
  atomic properties.

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Chapter 4. ATOMIC STRUCTURE AND THE
PERIODIC TABLE
Atomic Structure An atom is composed of three
types of subatomic particles the proton,
neutron, and electron.
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Atomic Structure
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Atomic Structure
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Electromagnetic Radiation
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Electromagnetic Radiation

• nl c
• Where
• n frequency
• l wavelength
• c speed of light

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Electromagnetic Spectrum
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Dispersion of White Light
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Photoelectric Effect

• the emission of electrons by substances,
  especially metals, when light falls on their
  surfaces.

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Photoelectric Effect
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Quantum Mechanics

• Quantum theory
• the theory of the structure and behavior of
  atoms and molecules.

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Photons

• The quantum of electromagnetic energy,
• generally regarded as a
• discrete particle having zero mass, no
• electric charge, and an indefinitely
• long lifetime.
• E h? hc/?
• h Planck's constant 6.626 10-34 J.s

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Line Emission Spectrum
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Absorption Spectrum

• Light shinning on a sample causes electrons
  to be excited from the ground state to an
  excited state
• wavelengths of that energy are removed from
  transmitted spectra

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The Atomic Spectrum of Hydrogen and the Bohr
Model

• Bohr Model for the Hydrogen Atom
• mvr nh/2p
• n quantum number
• n 1, 2, 3, 4, 5, 6, 7, etc

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Bohr Atom
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Ground State

• The state of least possible energy in a
  physical system, as of elementary particles. Also
  called ground level.

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Excited State

• Being at an energy level higher than the
  ground state.

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Electron Transition in a Hydrogen Atom
Lyman series ? ultraviolet n gt 1 ? n
1 Balmer series ? visible light n gt 2 ?
n 2 Paschen series ? infrared n gt 3 ?
n 3
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• Knowing diamond is transparent, which curve best
  represents the absorption spectrum of diamond
  (see below)?
• A, B, C

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• According to the energy diagram below for the
  Bohr model of the hydrogen atom, if an electron
  jumps from E1 to E2, energy is
• absorbed
• emitted
• not involved

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Orbitals

• region of probability of finding an electron
  around the nucleus
• 4 types s, p, d, f

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Atomic Orbitals, s-type
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Atomic Orbitals, p-type
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Atomic Orbitals, d-type
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Pauli Exclusion Principle
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Electronic Configurations

• The shorthand representation of the occupancy of
  the energy levels (shells and subshells) of an
  atom by electrons.

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Hund's Rules
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Electronic Configuration

• H atom (1 electron) 1s1
• He atom (2 electrons) 1s2
• Li atom (3 electrons) 1s2, 2s1
• Cl atom
• (17 electrons) 1s2, 2s2, 2p6, 3s2, 3p5

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Electronic Configuration

• As atom
• 33 electons
• 1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d10, 4p3
• or
• Ar 4s2, 3d10, 4p3

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• Mn Ar4s2 3d?
• How many d electrons does Mn have?
• 4, 5, 6

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Electronic Configuration

• Negative ions
• add electron(s), 1 electron for each
• negative charge
• S-2 ion (16 2)electrons
• 1s2, 2s2, 2p6, 3s2, 3p6

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Electronic Configuration

• Positive ions
• remove electron(s), 1 electron for each
• positive charge
• Mg2 ion (12-2) electrons
• 1s2, 2s2, 2p6

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• How many valence electrons are in Cl, Ne3s2
  3p5?
• 2, 5, 7

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• For Cl to achieve a noble gas configuration, it
  is more likely that
• electrons would be added
• electrons would be removed

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Regions by Electron Type
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Trends in the Periodic Table

• atomic radius
• ionic radius
• ionization energy
• electron affinity

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Atomic Radius

• decrease left to right across a period

Zeff Z - S where Zeff
effective nuclear charge Z nuclear charge,
atomic number S shielding constant
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Atomic Radius

• Increase top to bottom down a group
• Increases from upper right corner to the lower
  left corner

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Atomic Radius
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Atomic Radius vs. Atomic Number
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Ionic Radii
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Ionic Radius

• Same trends as for atomic radius
• positive ions smaller than atom
• negative ions larger than atom

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Comparison of Atomic and Ionic Radii
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Ionic Radius

• Isoelectronic Series
• series of negative ions, noble gas atom, and
  positive ions with the same electronic
  confiuration
• size decreases as positive charge of the
  nucleus increases

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Ionization Energy

• energy necessary to remove an electron to form a
  positive ion
• low value for metals, electrons easily removed
• high value for non-metals, electrons difficult to
  remove
• increases from lower left corner of periodic
  table to the upper right corner

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Ionization Energies

• first ionization energy
• energy to remove first electron from an atom.
• second ionization energy
• energy to remove second electron from a 1 ion.
• etc.

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Ionization Energy vs. Atomic Number
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Electron Affinity

• energy released when an electron is added to an
  atom
• same trends as ionization energy, increases from
  lower left corner to the upper right corner
• metals have low EA
• nonmetals have high EA

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Magnetism

• Result of the spin of electrons
• diamagnetism - no unpaired electrons
• paramagnetism - one or more unpaired electrons

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Magnetism
Without applied field
With applied field
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