CHM 1020

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CHM 1020

• Lecture 4
• Compounds Their Bonds

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• Octet Rule all elements want to have 8 valence
  electrons in order to be stable
• Ions charged particles resulting from the
  gain/loss of ELECTRONS.
• Cations
• Anions
• 1A 1 4A --- 7A -1
• 2A 2 5A -3 8A 0
• 3A 3 6A -2

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• Give the number of p,e,n for Ni 2? Sc 3?
• S-2? N-3?

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• Atoms
• Consist of 1 element
• Molecules (Molecular Compounds)
• 2 or more atoms that act as a unit
• Molecules
• Low melting boiling point
• Many exist as gases/liquid _at_ room temperature
• Formula Units (Ionic Compounds)
• Metal Nonmetal
• Cation Anion must be electrically neutral
• High melting/boiling point
• Brittle
• Dissolve in water
• electrolytes

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Ions

• 2 types
• Monatomic
• Cation
• Ex Ca 2, Li 1
• Name the element
• If you have a transition metal, YOU MUST use
  Roman Numerals to indicate the oxidation number
  (exceptions Ag, Zn, Pb, Sn)
• Anion
• O -2, N -3
• Drop the ending and add -ide
• Polyatomic Ions
• 2 or more atoms with a charge
• Ex SO4 -2, OH -1, PO4 -3
• Name the polyatomic ion as is

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Examples
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Binary Molecular Compounds

• 1. The first word is the name of the first
• element in the compound, modified with a
• prefix to indicate the number of atoms
• of that element in the molecule.
• 2. The second word is the name of the second
• element in the compound, changed to end in
• -ide, modified with a prefix to indicate the
• number of atoms of that element
• in the molecule.
• 3. H2O is water, NH3 is ammonia

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Prefixes

• 1 mono
• 2 di
• 3 tri
• 4 tetra
• 5 penta
• 6 hexa
• 7 hepta
• 8 octa
• 9 nona
• 10 deca

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Examples

• Name the following
• CO
• N2O
• Cl2O7
• PCl3
• SF6
• Cl2O8
• Nitrogen trifluoride
• Disulfur dichloride
• Sulfur trioxide
• Dinitrogen tetroxide

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Binary Ionic Compounds

• Naming
• Name the cation (Dont forget to use roman
  numerals)
• Name the anion
• If you have need Roman numerals
• Atoms X atomic charge
• Both ions need to have equal, but opposite
  charges (electrically neutral)
• Solve for the unknown variable
• Ex BaCl2, FeO, CoI3
• Writing Formulas
• Criss-cross the oxidation numbers of both the
  cation and anion (atoms)
• Simplify atoms

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• Writing formulas
• Cation Anion
• Ba 2 S -2

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2
atoms
simplify
1
1
Formula BaS Name
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• Cation Anion
• Cu 2 I -1

2
atoms
1
Formula Name
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Examples

• Li 1, O -2
• Ca 2, N -3
• Fe 2, S -2
• Potassium phosphide
• Aluminum sulfide
• Sodium iodide
• Iron (III) oxide
• Lithium fluoride
• Aluminum nitride

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Ternary Ionic Compounds (polyatomic ions)

• Consists of both covalent and ionic compounds
• Usually involves 3 or more elements
• Name will end in either ate, -ite (some
  exceptions such as hydroxide OH-1,NH4 1, CN -1)
• Writing formulas same as for binary ionic
  compunds, except that if you have 2 or more
  polyatomic ions, you need to enclose it in
  parentheses.
• Name the cation name of the polyatomic ion
• Ex KNO3
• Cation K? Potassium
• Polyatomic ion NO3 ? nitrate
• Name potassium nitrate

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Examples

• NH4Br
• Ca(OH)2
• CuSO4
• Cu2O
• Al(OH)3
• Sn3(PO4)2
• Copper (II) sulfate
• Barium nitrate

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Lewis Dot diagram

• Representation of valence electrons using dots
• Covalent Bonds
• Single
• Double
• triple

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Types of Chemical Bond

• 3 types of covalent bonding

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Bond Polarity
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Polar vs. Nonpolar

• Polar bond with uneven distribution of charge
  (dipole)
• Nonpolar atoms in a molecule are the same and
  bonding of electrons are equally shared. Ex
  diatomic molecules
• More electronegative atom acquires a slight
  negative charge and less electronegative atom
  acquires a slight positive charge

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VSEPR (molecular geometry)

• Valence shell electron pair repulsion
• Geometry of compounds
• Electron density
• Electron pairs repel one another. Therefore they
  distribute themselves in positions around the
  central atom that are as far away from each other
  as possible

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Steps

• Determine Central Atom
• Determine the number of valence pairs
• Atoms X group number (valence electrons)
• Divide the answer by 2
• Determine the number of lone pairs
• Valence pairs 4 (number of atoms bonded to the
  central atom)
• Valence pairs 1 (number of atoms bonded to the
  central atom)
• If you have a combination of H and something
  else, YOU MUST draw the Lewis structure
• Use ABxEy
• A central atom
• Bx number of atoms attached to the central atom
• Ey number of lone pairs

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Examples

• SCl2
• CO2
• NH3
• H2O
• CO3 -2
• NH4 1

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