Transcript Names & Formulas Ionic Compounds 8.3 Formulas  Formula unit is the ratio of cations to anions’ • Total number of electrons lost by cations must equal.

Names & Formulas
Ionic Compounds
8.3
Formulas

Formula unit is the ratio of cations to
anions’
• Total number of electrons lost by cations
must equal total number of electrons
gained by anions
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Binary compounds = simplest
compound = 2 atoms
• One cation, one anion
• Monatomic ion = ion made from one
atom
Typical Ions
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See Book, page 221
Oxidation number = oxidation state
= number of electrons transferred
from an atom to make a compound
• Na+ oxidation number = +1
• O2- oxidation number = 2• Used to determine compound formulas
Formula Names
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Remember: total number of electrons lost
by cations must equal total number of
electrons gained by anions!
Metal name is stated first.
• Number of cations in ratio is subcripted
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Nonmetal name is stated second
• Suffix –ide is used
• Number of anions in ration is subscripted
Formula Names
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Examples
• Sodium (Na+) and Chlorine (Cl-)
NaCl = ratio 1:1
Sodium Chloride
• Calcium (Ca2+) and Fluorine (Fl-)
CaFl2 = ratio 1:2
Calcium Fluoride
Aluminum (3+) and Sulfur (2-)
Find lowest common dominator
(6)
2(Al 3+) + 3 (S 2+) = both transfer 6 electrons
Al2S3
Aluminum Sulfide
Formulas with Polyatomic Ions
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Poly atomic ions stay together as a
single group
Example Calcium and Phosphate
• Calcium (2+)
• Phosphate PO4 (3-)
• 3 (Ca) + 2 ( PO4)
• Ca3(PO4)2
• Calcium Phosphate
Naming Polyatomic Compounds
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Oxyanions = polyatomic anions with one
or more oxygen atom
With 2 anion forms:
• Anion with most oxygen atoms is –ate
• Anion with fewer oxygen atoms is –ite
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With multiple anion forms:
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Most oxygen atoms is per- metal -ate
Second most oxygen is –ate
Third most oxygen atoms is –ite
Fourth most oxygen atoms is hypo- metal -ite
Naming Review
1.
2.
3.
4.
5.
Name cation first, anion second
Monatomic ions use atom name
Monatomic anions take root of name and
add –ide suffix
Group 1A and 2A metals have only one
oxidation state. Transition metals can
have more than one. Put oxidation state
in as roman numerals
Polyatomic ions – just name the ion