Ionic Bond: MetalMetal + NonmetalNonmetal

• Metals: lose valence electrons – formform cation cation (+ ion)

• Nonmetals: gain electrons –form anionanion (- ion)

IONIC BONDING

• Involves Involves transfer of electronstransfer of electrons– electrons go from metal to nonmetalelectrons go from metal to nonmetal

• # electrons# electrons Lost Lost by by CationCation (metal) (metal)

= =

# electrons # electrons GainedGained by by Anion (nonmetal)Anion (nonmetal)

Metals are losers!Metals are losers!

• Na has configuration 2-8-1

• Na loses 1 electron → Na+1 –Na+1 configuration is 2-8 (Ne)

• What can taketake the valence electron from Na??

Na metal Na metal

Nonmetals are winners!Nonmetals are winners!

• Cl has configuration 2-8-7

• Cl gains 1 electron → Cl-1

– Cl-1 configuration 2-8-8 (Ar)

• What can donatedonate an electron to Cl ??

ClCl22 (g) (g)

Electron is transferred from Na to ClElectron is transferred from Na to Cl

Structure of Ionic Compounds

• Ions are attracted to each other by strong electrostatic interactions (between +/- ions)

• Ions form crystal lattice – regular 3-D pattern or array – Ions are held in fixed positions (solid state)

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lattice structure lattice structure

NaCl has its own NaCl has its own unique propertiesunique properties

The more Na and ClThe more Na and Cl22, the , the larger the resulting NaCl larger the resulting NaCl crystal crystal

-just keep adding on to it-just keep adding on to it

Different Different representations of representations of a crystal latticea crystal lattice

Lewis Diagrams for Ionic Compounds

NaCl's Lewis structure:NaCl's Lewis structure:

[[NaNa]]+1 +1 [ [ Cl Cl ]]-1-1••••

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Remember: Lewis diagrams show valence electrons!Remember: Lewis diagrams show valence electrons!

Predicting Ionic Compounds

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

• Calcium - metal - 2 valence electrons Calcium - metal - 2 valence electrons - loses both electrons - loses both electrons [[CaCa]]+2+2

• Iodine - nonmetal - 7 valence electrons Iodine - nonmetal - 7 valence electrons - gains 1 electron - gains 1 electron [[ I I ]]-1-1

How many iodine ions do you need to make a How many iodine ions do you need to make a neutral compound?neutral compound? 22

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Lewis Diagram of Calcium iodide

Ca 2-8-8-2 → CaCa 2-8-8-2 → Ca+2+2 2-8-8 2-8-8I 2-8-18-18-7 → II 2-8-18-18-7 → I-1-1 2-8-18-18-8 2-8-18-18-8

[[CaCa]]+2+2[:[:II:]:]-1-1[:[:II:]:]-1-1 or [: or [:II:]:]-1-1[[CaCa]]+2+2[:[:II:]:]-1-1

Note: total charge adds up to zero Note: total charge adds up to zero

- compounds are neutral- compounds are neutral

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