# Ionic Formula writing Notes

```Naming
Ionic Compounds
Charges
Elements will gain or lose electrons to have 8 valence
electrons. (This is the octet rule)
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Group 1A  +1
Group 2A  +2
Group 3A  +3
Group 4A  N/A
Group 5A  -3
Group 6A  -2
Group 7A  -1
Group 8A  STABLE
• The charges of
monatomic ions, or
ions containing only
one atom, can be
determined by
referring to the
periodic table
Ionic Compounds
• ion : atom or group of atoms that has a charge
• A monatomic ion is one atom with a charge
• A polyatomic ion is more than one element with a
charge
• Example: SO42-
• ionic compound: compound formed between a
cation ( +) and an anion (-).
– usually between a metal and a nonmetal.
– also form between a polyatomic ion (like ammonium) and
either a metal or nonmetal.
• TRANSFER valence electrons
Formation of Ionic Compounds
• objects with opposite
charges attract each other.
• ionic bond = the strong
attractive force between ions
of opposite charge
– Strongest type of bond!!
• the overall charge of the
compound will be …
• ZERO!
Examples of Formula Writing
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Write the formula for the compound formed between calcium and nitrogen
• Step One: Write the symbols and charges of the
ions formed
– Ca2+ N3-
• Step Two: Criss Cross (Balance the charges so the
total is ZERO)
– You will need 3 Calcium’s and 2 Nitride’s
• Step Three: Write the Formula
– Use subscripts to show the number of each ion needed
–Ca3N2
– If the charge is &gt;1 than polyatomics need ()
More examples
• Write the formula between Mg and Br
• Mg+2 Br -1
• MgBr2
More examples
• Write the formula for the compound
formed between Ca and S
• Ca+2 S-2
• CaS
Polyatomic Ions
• You must use parentheses when using
subscripts with a polyatomic ion
• Ex: Calcium nitrate
• Ca +2 NO3 -1
• Ca(NO3)2
Formula writing with polyatomic
Ions
• Write the formula between ammonium
and sulfate
• NH4 +1 SO4 -2
• (NH4)2 SO4
More examples
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Copper (II) and chlorine
Silver and Nitrate
Magnesium and sulfite
Calcium and sulfur
Potassium and oxygen
Ammonium and phosphate
Ammonium and chlorine
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CuCl2
AgNO3
MgSO3
CaS
K2O
(NH4)3PO4
NH4Cl
Naming ionic compounds
• In naming ionic compounds, name the cation
first, then the anion.
• Cation name does not change.
– If the cation can have more than one charge
(mostly transition metals), use a Roman Numeral
after the element name to indicate the charge
• Ex. Iron (II) for Fe2+ or Iron (III) for Fe3+
• Monatomic anions: change the ending to -ide.
(ex. Br -, Cl-, O2-)
• Polyatomic Ions: do not change the name
(ex. SO42-, CO32-, PO43-
Examples
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NaCl
MgSO4
CuSO3
K3PO4
Fe(NO3)2
Ca(ClO3)2
NH4NO2
Al(ClO)3
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Sodium chloride
Magnesium sulfate
Copper (II) sulfite
Potassium phosphate
Iron (II) nitrate
Calcium chlorate
Ammonium nitrite
Aluminum hypochlorite
More examples
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Ammonium Permanganate
Cobalt (II) chloride
Calcium sulfide
Lithium nitrate
Sodium acetate
Tin (II) chloride
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PbO2
NH4MnO4
CoCl2
CaS
LiNO3
NaCH3COO
SnCl2
```