POLYATOMIC IONS &
NAMING IONIC
COMPOUNDS
Unit 5: Chapter 6.3a
BONDING REVIEW
• Ionic - electron transfer
– Forms between a metal and a nonmetal
• Metals have low electronegativity
• Nonmetals have high electronegativity
– The metal gives up the electrons and the
nonmetal takes them
• Covalent - electron sharing
– Forms most often between two nonmetals
– Electron shared pairs are formed to allow both
elements to fulfill the octet rule.
DESCRIBING IONIC
COMPOUNDS
• These objects are coated with compounds of
copper and oxygen. Based on the two colors of the
coatings, copper and oxygen must form at least
two compounds. So there must also be different
ways of naming them.
DESCRIBING IONIC
COMPOUNDS
• What information do the name and
formula of an ionic compound provide?
– The name distinguishes the compound from
other ionic compounds containing the same
elements.
– The formula of an ionic compound describes the
ratio of the ions in the compound.
BINARY IONIC COMPOUNDS
• A compound made from only two elements is a
binary compound.
• Naming binary ionic compounds is easy. The names
have a predictable pattern:
– the name of the cation (metal) followed by the
name of the anion (nonmetal).
– Examples:
• Na+ + Cl-  Sodium Ion + Chloride =
– Sodium Chloride
• K+ + O2-  Potassium Ion + Oxide =
–Potassium Oxide
COMMON ANIONS
• This table lists
eight common
anions.
– The name of
an anion is
formed by
adding the
suffix –ide to
the stem of
the nonmetal
name.
NAMING BINARY IONIC
COMPOUNDS
• Cations (metal) first, then Anion (non-metal)
• Cation (metal) name is normal
– Example: sodium
• Anion (nonmetal) add “ide” suffix
– Example: chlorine  chloride
• NaCl  sodium chloride
• KBr  potassium bromide
POLYVALENT METALS
• Many transition metals have “multiple
personalities”
– # of valence electrons varies
– they can form more than one ion (more than
one charge).
• Also known as valence # or oxidation #
• Roman Numerals are used to signify the charge (or
how many electrons the metal is lending)
• Where are the transition metals located on the
periodic table?
TRANSITION METALS
POLYVALENT TRANSITION
METALS
• Metals with more than one possible charge:
• Specific charge is indicated in parenthesis
POLYVALENT METALS &
BONDING
• Fe(II) = Fe2+
– Iron (II) + oxygen = Iron (II) Oxide
• Fe2+ & O2-  FeO
• Fe(III) = Fe3+
– Iron (III) + oxygen = Iron (III) Oxide
• Fe3+ & O2-  Fe2O3
• Name these compounds just like other
binary ionic compounds but include the
metal’s oxidation # in parentheses
POLYATOMIC IONS
• Polyatomic Ion - A covalently bonded group of
atoms that acts as a unit and has its own charge.
– Most simple polyatomic ions are anions.
• MUST keep the atoms together
• CANNOT change anything about a polyatomic ion
– Not the type of atoms
– Not the number of atoms
– Not the electric charge
• How are you going to remember this????
– Anytime you see a Polyatomic Ion
• PUT IT IN PARENTHESIS!!!
POLYATOMIC IONS
POLYATOMIC IONS & BONDING
• Bonding works the same way as it did for
binary compounds.
• Treat the polyatomic ion as a single entity (a
single element)
• The criss cross method is the most useful,
efficient, and effective way for bonding with
polyatomic ions.
CRISS CROSS METHOD
REVIEW
• Determine the charges/oxidation #’s for each
element.
• By criss crossing the charges of the elements you
can easily write the chemical formula
• Example: Hydrogen + Oxygen
– H+1 + O–2
– Criss cross the oxidation #
• just the numbers - not the + / - signs
– Write the numbers as subscripts
• bottom right of symbol
CRISS CROSS METHOD
REVIEW
H+1
O-2
Criss Cross the numbers
H2O1
Final:
H2O
• Where is the 1 in the final formula?
– Just like in math, the 1 is always understood.
CRISS CROSS & POLYATOMIC
IONS
• Sodium + Sulfate
– Na + SO4
– Na+1 + (SO4)-2
Do the Criss Cross
Na2(SO4)1
Final: Na2(SO4) or Na2SO4
YOU TRY
• Magnesium + Sulfate
– Mg + SO4
YOU TRY
• Magnesium + Sulfate
– Mg + SO4
– Mg+2 + (SO4)-2
YOU TRY
• Magnesium + Sulfate
– Mg + SO4
– Mg+2 + (SO4)-2
– Criss Cross
• Mg2(SO4)2
• Final: Mg(SO4) or MgSO4
– Remember the ratio can be reduced! (the
2’s reduce to 1:1)
YOU TRY
• Beryllium + Phosphate
– Be + PO4
YOU TRY
• Beryllium + Phosphate
– Be + PO4
– Be+2 + (PO4)-3
YOU TRY
• Beryllium + Phosphate
– Be + PO4
– Be+2 + (PO4)-3
– Criss Cross
• Be3(PO4)2
• Note that the criss cross puts the subscript 2
OUTSIDE of the parenthesis, showing that
there are TWO phosphate ions
Common Ions
Hydrogen H+1
Aluminum Al+3
Nitrate (NO3)-1
Calcium Ca+2
Iron (III) Fe+3
Sulfate (SO4)-2
Zinc Zn+2
Chlorine Cl-1
Carbonate (CO3)-2
Copper (II) Cu+2
Hydroxide OH-1
Phosphate (PO4)-3
Silver Ag+1
Phosphide P-3
Acetate (C2H3O2)-1
Which of these are:
•Metals?
•Nonmetals?
•Transition metals?
•Polyatomic ions?
NAMING WITH POLYATOMIC
IONS
• Compounds containing polyatomic Ions always
have IONIC bonds.
• Naming these compounds is much like naming
binary ionic compounds
– List the cation (metal) first
– Then the polyatomic ion (most are anions so this
follows the binary format)
– Use the normal name for the cation (metal) and
the given name for the polyatomic ion
• Na(OH) or NaOH = Sodium Hydroxide
FORMULAS & NAMES
• Use a compound’s formula to determine its name
– Na2O  Sodium Oxide
– CuF2  Copper (II) Fluoride
– K2(CO3)  Potassium Carbonate
• Use a compound’s name to determine its formula
– Lithium Bromide  LiBr
– Iron (III) Oxide  Fe2O3
– Aluminum Phosphate  Al(PO4) or AlPO4
• You must be able to go back and forth!
YOU TRY
• Write the formula for
– Calcium Chloride
– Calcium Oxide
– Copper (II) Nitride
– Magnesium Sulfate
• Give the name for the following compounds
– KBr
– BeS
– PbO2
– CsMnO4
YOU TRY
• Write the formula for
– Calcium Chloride  CaCl2
– Calcium Oxide  CaO
– Copper (II) Nitride  Cu3N2
– Magnesium Sulfate  MgSO4
• Give the name for the following compounds
– KBr  Potassium Bromide
– BeS  Beryllium Sulfide
– PbO2  Lead (IV) Oxide
– CsMnO4  Cesium Permanganate