Naming & Formulas:
Multivalent & Polyatomic Ions
Multivalent Metals
• Multi = multiple
• Valent = charge
• Metal = specifically transition metals
 List all of the possible valencies for the following metals:
Metal
Possible valencies:
Metal
Cu
Fe
Pb
Mn
V
Ti
Hg
Cr
Mo
W
Possible valencies:
Naming Multivalent Metals
Rule:
• Indicate the charge in the name by a roman
numeral
• Metals are always a positive charge
Naming Multivalent Metals
• Example 1: CuO
1. Identify the positive ion and the negative ion
Cu2+ – positive ion (how do we know that it has a charge of 2+?)
O2- – negative ion
2. What is the name of the positive ion?
Cu2+ - copper (II)
3. What is the name of the negative ion? –
change the ending to “ide”
O2- - oxide
CuO = copper (II) oxide
Naming Multivalent Metals
• Example 2: Cu2O
1. Identify the positive ion and the negative ion
Cu+ – positive ion (how do we know that it has a charge of 1+?)
O2- – negative ion
2. What is the name of the positive ion?
Cu+ - copper (I)
3. What is the name of the negative ion? –
change the ending to “ide”
O2- - oxide
Cu2O = Copper (I) oxide
Naming Multivalent Metals
• Example 3: PtCl4
1. Identify the positive ion and the negative ion
Pt4+ – positive ion
Cl- – negative ion
2. What is the name of the positive ion?
Pt4+ – platinum (IV)
3. What is the name of the negative ion? – change
the ending to “ide”
Cl- - chloride
PtCl4 = platinum (IV) chloride
Naming Multivalent Metals
Naming Polyatomic Ions
• Poly = many
• Atomic = atoms
• Ions = with charge
• *All Polyatomics are listed in your Data Booklets p. 5
Polyatomic Ion
Name
Charge
hydroxide
PO43acetate
NO3hypochlorite
1+
CrO4 2dichromate
Naming Polyatomic Ions
• Poly = many
• Atomic = atoms
• Ions = with charge
• *All Polyatomics are listed in your Data Booklets p. 5
Polyatomic Ion
Name
Charge
OH-
hydroxide
1-
PO43-
phosphate
3-
CH3COO-
acetate
1-
NO3-
nitrate
1-
ClO-
hypochlorite
1-
NH4+
ammonium
1+
CrO4 2-
chromate
2-
Cr2O7 2-
dichromate
2-
Naming Polyatomic Ions
• Example 1: NH4Cl
1. Identify the positive ion and the negative ion
NH4+ – positive ion
Cl- – negative ion
2. What is the name of the positive ion?
NH4+ – ammonium
3. What is the name of the negative ion? –
change the ending to “ide”
Cl- - chloride
NH4Cl = ammonium chloride
Naming Polyatomic Ions
• Example 2: KNO3
1. Identify the positive ion and the negative ion
K+ – positive ion
NO3- – negative ion
2. What is the name of the positive ion?
K+ – potassium
3. What is the name of the negative ion? – change
the ending to “ide” unless it is a polyatomic ion!
NO3- - nitrate
KNO3 = potassium nitrate
Naming Polyatomic Ions
• Example 3: Cu(OH)2
1. Identify the positive ion and the negative ion
Cu2+ – positive ion
OH- – negative ion
2. What is the name of the positive ion?
Cu2+ – copper (II)
3. What is the name of the negative ion? – change
the ending to “ide” unless it is a polyatomic ion!
OH- - hydroxide
Cu(OH)2 = copper (II) hydroxide
Formulas of Polyatomic Ions
• Example 1: Magnesium sulphate
1. What is the charge of magnesium?
2+
2. What is the charge of sulphate?
23. To write the formula, we must balance the charges.
Positive
Mg2+
Negative
SO42-
Overall: 2+
Overall: 2MgSO4
Formulas of Polyatomic Ions
• Example 2: Strontium nitrate
1. What is the charge of strontium?
2+
2. What is the charge of nitrate?
13. To write the formula, we must balance the charges.
Positive
Sr2+
Negative
NO3- NO3-
Overall: 2+
Overall: 2Sr(NO3)2
Formulas of Polyatomic Ions
• Example 3: Calcium hydroxide
1. What is the charge of calcium?
2+
2. What is the charge of hydroxide?
13. To write the formula, we must balance the charges.
Positive
Ca2+
Negative
OH- OH-
Overall: 2+
Overall: 2Ca(OH)2
Naming Polyatomic Ions
In-Class Work
• CYU 7.3 Q’s 2-5