Naming and Writing IONIC Chemical Formulas
Chem Lab Methods
Chemical Symbols
Chemical Formulas: Writing
Use the chemical symbol for each element
Usually, the element abbreviations come from the word
(He for Helium or Ti for Titanium)
Some elements have just one letter, such as H for Hydrogen or N for Nitrogen
Chemical Formulas: Writing
Most elements have two letters Always capitalize the first letter and
use lower case on the second one.Example: Cobalt is Co
If you used two capitals (CO), it would be mistaken for Carbon Monoxide which has one Carbon (C) and one Oxygen (O)
Chemical Formulas: Subscripts
The subscript number specifies how many atoms of that element you have
N2 is a nitrogen molecule with two atoms
C2H4 has two carbons and four hydrogens
CO2 contains one carbon and two oxygens
If no number is listed, it means there is only one
Example
C2H3Cl what elements and how many of each?
Example
C2H3Cl what elements and how many of each?
Example
H2SiCl2what elements and how many of each?
Example
H2SiCl2what elements and how many of each?
Chemical Formulas: Coefficients (numbers in front)
CH4 what elements and how many of each?
Chemical Formulas: Coefficients (numbers in front)
CH4 => methanewhat elements and how many of each?
Chemical Formulas: Coefficients (numbers in front)
When there are large numbers in front, that tells you how many molecules there are.
For example 3CH4 =
Chemical Formulas: Coefficients (numbers in front)
When there are large numbers in front, that tells you how many molecules there are.
For example 3CH4 = 3 methane molecules
12NaOH = ?
Chemical Formulas: Coefficients (numbers in front)
When there are large numbers in front, that tells you how many molecules there are.
For example 3CH4 = 3 methane molecules
12NaOH = 12 different Sodium Hydroxide units
Practice
Counting Atoms
Definitions
Nomenclature: Choosing of names for things Naming procedure
Ionic Compound: Atoms held together by ionic bonds
Binary Compound: Chemical compound made of atoms
from two different elements
Naming: Binary Ionic Compounds
Metal element name first
Then the non-metal element name, but the ending is changed to -ide
Example: CaCl2 would be called calcium chloride
Example: Ag2O would be called… silver oxide
Practice
Naming Binary Compounds
Ionic Formulas: Developing
Example:
Compound name - Magnesium chloride …What is the formula?
Ionic Formulas: Developing
Magnesium Chloride =
Mg+2 Cl-1
What charge ion would each atom
form?
How many of each to make a neutral compou
nd?
Ionic Formulas: Developing Magnesium Chloride: Mg+2 and Cl-1
The charge of the final compound must be neutral.(The charges must balance)▪ Need TWO Cl-1 ions to balance one Mg+2 ion▪ (2 x -1) = (1 x +2) = 2 minus balances 2 plus
(Criss Cross!) Mg1 Cl2
MgCl2
Ionic Formulas: Developing
Magnesium Chloride = 1 Mg+2 + 2 Cl-1 => MgCl2
Mg+2 Cl-1
Ionic Formulas: Developing
Example: Compound name Lithium sulfide …What is the formula?
Ionic Formulas: Developing
Lithium Sulfide=
Li+1S-2
What charge ion would each atom
form?
How many of each to make a neutral compou
nd?
Ionic Formulas: Developing Magnesium Chloride: Li+1 and S-2
The charge of the final compound must be neutral.(The charges must balance)▪ Need TWO Li+1 ions to balance one S-2 ion▪ (2 x +1) = (1 x -2) = 2 minus balances 2 plus
(Criss Cross!) Li2 S1
Li 2 S
Ionic Formulas: Developing
Lithium sulfide = 2 Li+1 + 1 S-2 => Li2S
Li+1
S-2
Ionic Formulas: Developing
Example: Compound name Aluminum oxide …What is the formula?
Ionic Formulas: Developing
Aluminum Oxide=
Al+3O-2
What charge ion would each atom
form?
How many of each to make a neutral compou
nd?
Ionic Formulas: Developing Aluminum Oxide: Al+3 and O-2
The charge of the final compound must be neutral.(The charges must balance)▪ Need TWO Al+3 ions to balance THREE O-2 ions▪ (2 x +3) = (3 x -2) = 6 minus balances 6 plus
(Criss Cross!) Al2 O3 Al 2 O3
Ionic Formulas: Developing
Boron Oxide = 2 Al+3 + 3 O-2 => Al2O3
B+3 O-2
Ionic Formulas: Developing
SUMMARY of approach: Determine what charge ion would
form from each element Decide how many of each charge are
needed to have a balanced (neutral) formulaOR do “Criss Cross”
Write formula Subscripts state how many of each ion
are needed
Ionic Formulas: KEY POINT
Ionic compound formula describes: One “unit” of the chemical
compound Thus, it is called a “formula unit”
Important definition Example: 3 CaCl2
Three “formula units” of calcium chloride
Practice
Writing (Balanced) Chemical Formulas
Ionic Formulas: Continued….
Two more details:
Complex ions: contain more than one element
Transition metals: ionic charges can vary
Ionic Formulas: Complex Ions
Examples: Acetate is (C2H3O2)-1
▪ Whole group has -1 ionic charge
Carbonate is (CO3 )-2
▪ Whole group has -2 ionic charge
The ENTIRE group has one ionic charge
Acts like a single-atom ion of the same charge
List of common complex ions on the back of your periodic table
Ionic Formulas: Complex Ions
All but ONE of the common complex ions are negative Phosphate is (PO3)-3
▪ Whole group has -3 ionic charge
Chlorate is (ClO3 )-1
▪ Whole group has -1 ionic charge
THE positive complex ion (worth memorizing) is: Ammonium (NH4)+1
Ionic Formulas: Developing Magnesium Phosphate: Mg+2 and (PO4)-3
The charge of the final compound must be neutral.(The charges must balance)▪ Need THREE Mg+2 ions to balance TWO (PO4)-3 ions
▪ (3 x +2) = (2 x -3) = 6 minus balances 6 plus
(Criss Cross!) Mg3 (PO4) 2
Mg 3 (PO4)2
Ionic Formulas: Transition Metals
Ionic charge can vary
How do you know? Listed on Periodic Table “Clue” in name
Examples of naming for metals with multiple charges
Element Cation Name Pronounced
Copper Cu+
Cu2+
Iron Fe2+
Fe3+
Lead Pb2+
Pb4+
Tin Sn2+
Sn4+
Examples of naming for metals with multiple charges
Element Cation Name Pronounced
Copper Cu+ Copper (I) copper one
Cu2+
Iron Fe2+
Fe3+
Lead Pb2+
Pb4+
Tin Sn2+
Sn4+
Examples of naming for metals with multiple charges
Element Cation Name Pronounced
Copper Cu+ Copper (I) copper one
Cu2+ Copper (II) copper two
Iron Fe2+
Fe3+
Lead Pb2+
Pb4+
Tin Sn2+
Sn4+
Examples of naming for metals with multiple charges
Element Cation Name Pronounced
Copper Cu+ Copper (I) copper one
Cu2+ Copper (II) copper two
Iron Fe2+ Iron (II) iron two
Fe3+ Iron (III) iron three
Lead Pb2+
Pb4+
Tin Sn2+
Sn4+
Examples of naming for metals with multiple charges
Element Cation Name Pronounced
Copper Cu+ Copper (I) copper one
Cu2+ Copper (II) copper two
Iron Fe2+ Iron (II) iron two
Fe3+ Iron (III) iron three
Lead Pb2+ Lead (II) lead two
Pb4+ Lead (IV) lead four
Tin Sn2+ Tin (II) tin two
Sn4+ Tin (IV) tin four
Ionic Formulas: Transition Metal Example
Write the chemical formula for Iron (II) Oxide
Step One: Determine the charges Iron (II) = Fe2+ and Oxide = O2-
Step Two: See how to balance the charges
Step Three: Find the combination that balances
Iron (II) Oxide = FeO
Ionic Formulas: Transition Metal Example
Write the chemical formula for Lead (II) Nitride
Step One: Determine the charges Lead (II) = Pb+2 and Nitride = N-3
Step Two: See how to balance the charges
Step Three: Find the combination that balances
Lead (II) Nitride = Pb3 N2
How do you know if you use Roman numerals? Do not use Roman Numerals for groups 1 or 2 as
they are always (+1) and (+2) accordingly.
K = +1 and Ca = +2+1
+2
How do you know if you use Roman numerals? Do not use Roman numerals for transition
metals that always form the same charge ion. Ag = +1 and Zn = +2 and Cd = +2
Practice
Ionic Compound Formula Writing (all types)