Ionic Bonding and Salts 5.2

Ionic Bonds Chlorine gains 1 e- and sodium loses 1 e- Cl- and Na+ opposites attract Forms ionic bond Salt – an ionic compound that forms when a metal atom or a positive radical replaces the H of an acid

Ionic Compounds Ionic cmpds are electrically neutral Ions attract multiple opposite charged ions Form crystals

Energy Changes and Bonds E is required to Make Na a gas Remove an electron from Na Separate Cl molecule E is released when An e- is added to Cl Na+ and Cl- ions come together

Energy Changes Lattice Energy – the energy associated with a crystal lattice relative to the energy of all constituent atoms separated by infinite distances NaCl lattice E is higher than the amt. of E needed for previous steps in making NaCl = spontaneous rxn

Energy Changes Lattice Energy changes for each compound Lattice E needs to be overcome to break that bond as well NaCl in water/MgO in water

Are not molecules – more like crystals Charge balances out 1 Cl=1 Na Ionic Compounds Are not molecules – more like crystals Charge balances out 1 Cl=1 Na Very strong ionic bonds Very high melting and boiling points

Can’t conduct as solids – current can’t move Ionic Compounds Can’t conduct as solids – current can’t move Can conduct when melted or dissolved – current can move Hard and brittle Typically solid at room temp

Depends on size and # of ions Salt Crystals Crystal Lattice – the regular repeating pattern in which a crystal is arranged Depends on size and # of ions

Unit Cell Unit Cell – the smallest portion of a crystal lattice that shows the 3-D pattern of the entire lattice