Ionic Compounds
Neutral compound composed of cations and anions.
Total positive charge = Total negative charge
Table salt =
Na+ and Cl- ions
arranged in an alternating pattern
crystal lattice
Can react sodium metal with chlorine gas.
Sodium atoms lose electrons
Transferred to the chlorine atoms that gain electrons.
Gives off heat and even be explosive.
Note: Pure sodium metal is the elemental, uncharged
form: Na (11 protons, 11 electrons)
Pure chlorine gas is the elemental form. It is
diatomic: Cl2 (each atom 17 protons, 17
electrons)
Sodium ion: Na+ (11 protons, 10 electrons)
Chloride ion: Cl- (17 protons, 18 electrons)
For Ionic Compounds
 No molecules - no unique groups of atoms
 Ions arrange in an alternating pattern of cations &
anions
 Each ion surrounded by oppositely charged
ions
 Surrounded by as many as can accommodate
 Crystal lattice (array)
 Many kinds of patterns of alternation
 Crystals – one continuous array of ions
Names and Formulas
 (Cation) (Anion)
 Subscripts for ratio to give a neutral compound
based on ion charges (empirical formula only)
 Examples:
Na+ & ClNaCl sodium chloride (table salt)
Mg2+ & ClMgCl2
magnesium chloride
Mg2+ & PO43
Mg3(PO4)2 magnesium phosphate
 Use parentheses on polyatomics when have more
than one needed in the formula
 Note: Ionic compounds - no prefixes
Polyatomic Ion Names -The Details
• Polyatomic anions containing oxygen with more
than two members in the series are named as
follows (in order of decreasing oxygen):
per-….-ate
most oxygens
like "hyper", "per" indicates "more"
-ate
-ite
hypo-….-ite least oxygens
"hypo" means "less"
Example: Cl- (no oxygens)
ClO4- (most oxygen)
ClO3ClO2ClO- (least oxygen)
chloride ion
perchlorate ion
chlorate ion
chlorite ion
hypochlorite ion
Polyatomic Ions made by Adding Hydrogens (but
still have a polyatomic ION)
Polyatomic anions derived by adding H+ to an oxygen
containing polyatomic ion are named by adding as a
prefix the word hydrogen- or dihydrogen-.
SO42HSO4-
sulfate ion
Hydrogensulfate ion
PO43H2PO4-
phosphate ion
Dihydrogenphosphate ion
CO32HCO31-
carbonate ion
hydrogen carbonate ion OR
biocarbonate ion
Inorganic Acids
• Acids – can be formed when H+ added to an anion
to give a neutral compound
• The names of acids are related to the names of
anions:
•
-ide becomes hydro-….-ic acid;
-ate becomes -ic acid;
-ite becomes -ous acid.
ClHCl
chloride ion
hydrochloric acid
SO32H2SO3
Sulfite ion
Sulfurous Acid
SO42H2SO4
Sulfate ion
Sulfuric Acid
NO3HNO3
Nitrate ion
Nitric Acid