writing names and formulas for binary ionic compounds · writing names and formulas for binary...
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Writing Names and Formulas
for Binary Ionic Compounds
Chemical FormulasChemical Formulas tell us what and
how many elements are in a compound
NaCl
1 Na atom
1 Cl atom
SubscriptsSubscripts, written after the
element, identify the number of
atoms there are of each element.
H2O
2 H atoms
1 O atom
ParenthesisMultiply each atom in parenthesis by
the subscript outside of the parenthesis
(NH4)3PO4
3 Nitrogen atoms
12 Hydrogen atoms
1 Phosphorus atom
4 Oxygen atoms
Familiar Compounds
Sand
SiO2
Cane Sugar
C12H22O11
Lime
CaO
3 atoms 45 atoms 2 atoms
Writing Formulas
Binary ionic compounds have only two
types of ions
Even though the ions carry a
charge, the compounds are neutral
The number of negative ions must
equal the number of positive ions
Formula Writing Rules
1. Write the symbol and positive
oxidation numbered element
first
Magnesium Nitride
Mg +2
Representative Elements
Formula Writing Rules
2. Write the symbol of the element
that has the negative oxidation
number or charge
Magnesium Nitride
Mg + 2 N -3
Representative Elements
Formula Writing Rules
3. Write oxidation numbers of each
element, minus the charge, as the
subscript for the other element.
(Criss Cross)
Magnesium Nitride
Mg + 2 N -3
Mg3N2
Representative Elements
Writing Names
1. Write the full name of the positive ion
NaCl
Sodium
2. Write the root name of the negative ion
NaCl
Sodium Chlor
Representative Elements
Writing Names
3. Add the ending ide to the root
NaCl
Sodium Chloride
Practice
BaF2 KBr Al2O3
Representative Elements
Barium Fluoride
Potassium Bromide
Aluminum Oxide
Transition Metals
Recall that transition metals can have
more than one charge.
Transition Metals
Use roman numerals to denote the
charge
Fe+2 or Fe+3
Iron (ll) Chloride Iron (lll) Chloride
FeCl2 FeCl3
Transition Metals
Writing Names
1. Write the full name of the transition
metals
PbO2
Lead
Transition Metals
Writing Names
2. Figure out the charges of the anions
PbO2 2 x O-2 = - 4
Write the equivalent number of the
anion charges as a roman numeral
after the transition metal’s name
3.
Lead (IV)
Transition Metals
Writing Names
PbO2
Add the ending ‘ide’ to the anion 3.
Lead (IV) Oxide
Practice
CuBr CuBr2
Copper (I) Bromide Copper (II) Bromide
Transition Metals
Writing Formulas
1. Figure out the charge on the anion
Chromium (II) Sulfide
Sulfide S-2
2. Compare the anion’s charge to the
roman numeral on the transition metal
Cr (II) = +2 Sulfide S-2
Transition Metals
Writing Formulas
Adjust the subscripts so that
charges on the transition metal are
equal to the anion’s total charge
3.
CrS
Sulfide S-2Chromium (II) Cr+2
Transition Metals
Writing Formulas
More Practice
Sulfide S-2
Chromium (III) Sulfide
1. Figure out the charge on the anion
Transition Metals
Writing Formulas
2. Compare the anion’s charge to the
roman numeral on the transition metal
Chromium (III) +3
S - 2 Cr +3
Cr +3 S - 2
S - 2
Sulfide S-2
+6-6
Transition Metals
Writing Formulas
Adjust the subscripts so that
charges on the transition metal are
equal to the anion’s total charge
3.
Cr2S3
Chromium (III) Sulfide
2(Cr +3) 3(S - 2)