• metals: lose valence electrons
–form cation (+ ion)
• non-metals: gain electrons
–form anion (- ion)
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)
Metals are Losers!
• Na atom configuration: 2-8-1
• Na loses 1 electron → Na+1 ion
–Na+1 configuration is 2-8
• same as Ne configuration (2-8)
Na metal 
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
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)
Cl2 (g) 
electron transferred from Na to Cl
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
NaCl has its own
unique properties
lattice structure 
The more Na and Cl2, the
larger the resulting crystal of
NaCl will be
different representations
of a crystal lattice
Lewis Diagrams for Ionic
Compounds
Lewis structure for NaCl shows ions:
••
•
• -1
+1
[Na] [ •Cl •]
••
remember: Lewis diagrams show valence electrons!
Predicting Ionic Compounds
• What is the ionic compound formed from
calcium and iodine?
• calcium: metal with 2 valence electrons
- loses both electrons  [Ca]+2
• iodine: non-metal with 7 valence
electrons
•• -1
- gains 1 electron  [•• I ••]
••
• how many iodine ions are needed to make a
neutral compound?
2
Lewis Diagram of calcium iodide
(CaI2)
·· -1 ·· -1
+2
[Ca] [:I:] [:I:]
··
··
or
·· -1
··
+2
-1
[:I:] [Ca] [:I:]
··
··
note: total charge MUST add up to zero
since compounds are neutral
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
#1:
transfer of e- from
metal to non-metal
atoms: IONS form
#2:
electrostatic
attraction between
+/- ions leads to
ionic bond