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Chapter 8
Ionic Compounds: Names and Formulas
8.1 - Writing Chemical Formulas
Chemical Formulas - identify a compound by showing elements and their ratio
*Note: When non-metals and metals form a compound, metals come FIRST
Polyatomic Ions - groups of atoms occurring together in a compound
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Usually charged (like ions)
Mostly negative (behave as non-metals)
If positive, behaves as metal
Treated like a single atom’s ions
Some compounds with polyatomic ions:
How compounds look visually:
Writing and decoding chemical formulas:
Homework: pg. 237 - # 1 - 8
8.2 - Ion Charge and the Formulas of Ionic Compounds
Law of Definite Proportions:
A specific compound always contains the same elements in definite proportions.
Ionic compounds:
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Electrons transfered
Ions formed
Bonded by electrical force
Electrically neutral (same amount of + and - charges)
Between Metal and Non-metal
• Metal gives electron to Non-metal
Remember:
The total number of electrons transferred to form a single unit of the
compound will be the lowest common multiple (LCM) of the two ion charges
Formulas for Ionic Compounds with 2 Elements Combining
Elements combine in a 1:1 ratio
The total number of electrons transferred to form a single unit of the
compound will be the lowest common multiple (LCM) of the two ion charges
Quick Trick to Balance Charges
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Write the metal and non-metal elements in their ion form
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Write the metal and non-metal elements again, without charges
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Bring the charges down, criss-crossing them
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If the charges are the same, they simplify to ONE.
Formulas for Ionic Compounds with Polyatomic Ions
Same as previous case, but treat the polyatomic ion just like an individual element
Formulas for Ionic Compounds with More than One Ion Charge
Monovalent - an element with only ONE charge
Multivalent - an element with MULTIPLE charges
ONLY occur after atomic number 20
Homework: pg. 244 - # 1 - 13