metals: lose valence electrons

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• metals lose valence electrons
• form cation ( ion)
• non-metals gain electrons
• form anion (- ion)

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Ionic Bond

• occurs between
• metal element non-metal element
• involves transfer of electrons between metal
  non-metal elements to form ions
• electrons lost by cation(s)
• electrons gained by anion(s)

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Metals are Losers!

• Na atom configuration 2-8-1
• Na loses 1 electron ? Na1 ion
• Na1 configuration is 2-8
• same as Ne configuration (2-8)

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Na metal ?
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elements from what group _?_ will easily take the
one valence electron from Na??
what group has 7 valence electrons so only need
one more?
group 1 elements will easily give up their one
valence electron to the elements in group 17
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Non-metals are Winners!

• Cl configuration 2-8-7
• Cl gains 1 electron ? Cl-1 ion
• Cl-1 has the configuration 2-8-8
• same as Ar configuration (2-8-8)

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Cl2 (g) ?
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electron transferred from Na to Cl
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Structure of Ionic Compounds

• oppositely charged ions are attracted to each
  other by strong electrostatic interactions (/-)
• (/-) ions form crystal lattice
• regular 3-D pattern or array
• ions held in fixed positions (solid state)
• Unit Cell smallest repetitive unit in lattice

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NaCl has its own unique properties
lattice structure ?
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The more Na and Cl2, the larger the resulting
crystal of NaCl will be
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different representations of a crystal lattice
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Lewis Diagrams for Ionic Compounds

• Lewis structure for NaCl shows ions
• Na1 Cl -1

remember Lewis diagrams show valence electrons!
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Predicting Ionic Compounds

• What is the ionic compound formed from calcium
  and iodine?

• calcium metal with 2 valence electrons
• - loses both electrons ? Ca2

• iodine non-metal with 7 valence electrons
• - gains 1 electron ? ?I -1

• how many iodine ions are needed to make a
  neutral compound?

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Lewis Diagram of calcium iodide (CaI2)

• Ca2I-1I-1
• or
• I-1Ca2I-1
• note total charge MUST add up to zero
• since compounds are neutral

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Properties of Ionic Compounds

• high melting points
• low vapor pressures
• tend to be hard and brittle
• solids do not conduct electricity
• molten (liquid) states do conduct electricity
• aqueous solutions do conduct electricity

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1 transfer of e- from metal to non-metal atoms
IONS form 2 electrostatic attraction between
/- ions leads to ionic bond