Chemical Bonding Topic 5

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Chemical BondingTopic 5
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Metallic Bonding

• Occurs in metal samples
• Copper and brass for example
• Atoms involved lose valence e-
• Forming ions immersed in a sea of e-

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Metallic Solids

• Metallic solids have certain properties due to
  these free, mobile e-
• Malleable (hammered into thin sheet)
• Ductile (drawn into wire)
• Good conductors of heat and electricity (s, l, g)
• Lustrous (shiny)
• Generally hard
• Generally high mp bp

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Ionic Bonding

• Occurs between metal and nonmetal atoms due to
  transfer of e-
• NaCl and MgO for example
• The metal loses e- forming a ion
• The nonmetal gains e- forming a ion
• The oppositely charged ions are attracted to each
  other forming the ionic bond

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Ionic Solids

• Ionic solids have certain characteristics due to
  the crystal lattice formed by the and - ions
• Poor conductors as solids (good as l, g, aq)
• Generally hard
• Generally high mp

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Covalent Bonding

• Occurs between nonmetal atoms
• HCl and CO2 for example
• Involves the sharing of e- between atoms
• Sharing may be
• Equal (Nonpolar covalent, Cl2)
• Unequal (Polar covalent, HCl)
• Moocher (Coordinate covalent, NH4)

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Covalent Solids2 types

• Molecular Solids
• Poor conductors (s, l, g, aq)
• Soft
• Low mp
• Examples ice (H2O), sugar (C12H22O11), dry ice
  (CO2)

• Network Solids
• Poor conductors (s, l, g, aq)
• Hard
• High mp
• Examples sand (SiO2), graphite, diamond,
  asbestos, SiC

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Polar and Nonpolar Molecules

• Polar Molecules
• Uneven distribution of charge
• Have a end and a - end
• Asymmetrical shape
• Examples H2O, HCl, NH3

• Nonpolar Molecules
• Even distribution of charge
• No opposite ends
• Symmetrical shape
• Examples CO2, H2, CH4

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Forces of Attraction Between Molecules

• Dipole-Dipole attraction occurs between polar
  molecules, the end of one molecule is attracted
  to the end of another, throughout the sample.
• Hydrogen Bonding is a type of dipole-dipole
  attraction between molecules containing hydrogen
  such as H2O, NH3, and HF. Accounts for
  properties of water.

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Forces of Attraction continued

• Weak Intermolecular Forces (van der Waals
  London Dispersion) of attraction occur between
  nonpolar molecules due to momentary uneven
  distribution of charge as electrons move around.
  
• Molecule-Ion Forces of attraction occur between
  polar molecules and dissolved ions. NaCl(aq) for
  example.