Essay about Chem Review

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Review I

Review I: Chemical Compounds, Formulas, and Names
CHEM 1A Dr. Preeti Srinivasan Evergreen Valley College

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Formulas Describe Compounds
• A compound is a distinct substance that is composed of atoms of two or more elements. • Describe the compound by describing the number and type of each atom in the simplest unit of the compound.
– molecules or ions

• Each element is represented by its letter symbol. • The number of atoms of each element is written to the right of the element as a subscript.
– If there is only one atom, the 1 subscript is not written.

• Polyatomic groups are placed in parentheses.
– if more than one

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Classification of Compounds
Binary With 2 elements 1. Metal (fixed ionic charge), monoatomic anion 2. Metal (variable ionic charge), monoatomic anion 3. H monoatomic anion (acid) 4. Nonmetal nonmetal

Ternary
With 3 elements 1. Metal (fixed ionic charge), polyatomic anion 2. Metal (variable ionic charge), polyatomic anion 3. H polyatomic anion (acid) 4. Metal H polyatomic anion (acid salt)

• #1 and #2 in binary and #1, #2, and #4 in ternary compounds are also called as ionic compounds while the others are 3 molecular compounds.

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Review I

Metal Cations
• metals with fixed charge – metals whose ions can have only one possible charge • Groups 1A1+ & 2A2+, Al3+, Ag1+, Zn2+, Sc3+ – cation name = metal name

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• metals with variable charges  metals whose ions can have more than one possible charge  determine charge of cation by charge on anion  name = metal name with Roman numeral charge in parentheses (IUPAC name)

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Metal Cations (Contd.)
Trivial or common name
• Use the suffix -ic for the higher oxidation number and -ous for the lower oxidation number. • The -ic and -ous endings have no numerical representation.

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Review I

Naming Monatomic Nonmetal Anion
• Determine the charge from position on the Periodic Table. • To name anion, change ending on the element name to -ide. 4A = 4− C = carbide 5A = 3− N = nitride 6A = 2− O = oxide 7A = 1− F = fluoride

Si = silicide P = phosphide S = sulfide Cl = chloride
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Binary Ionic Compounds #1, #2
Compound must have no total charge; therefore, we must balance the numbers of cations and anions in a compound to get 0 charge. Rules for Writing Formulas for Binary Ionic Compounds
1. 2. 3. 4. 5. Write the symbol for the metal cation and its charge. Write the symbol for the nonmetal anion and its charge. Charge (without sign) becomes subscript for other ion. Reduce subscripts to smallest whole number ratio. Check that the sum of the charges of the cation cancels the sum of the anions.
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Learning Check
What are the formulas for compounds made from the following ions? potassium ion with a nitride ion

calcium ion with a bromide ion

aluminum ion with a sulfide ion
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Review I

Rules for Naming Binary Ionic Compounds
• made of cation and anion • Some have one or more nicknames that are only learned by experience.
– NaCl = table salt, NaHCO3 = baking soda

• Write IUPAC name by simply naming the ions.
– if cation is:
• metal with fixed charge = metal name • metal with variable charge = metal name(charge)

– for anion:
• nonmetal = stem of nonmetal name + -ide

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Naming Binary Ionic Compounds for Metals with Fixed Charge
• • contain metal cation + nonmetal anion metal listed first in formula and name

1. name metal cation first, name nonmetal anion second 2. cation name is the metal name 3. nonmetal anion named by changing the ending on the nonmetal name to -ide

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Learning Check
Name the following compounds. 1. 2. 3. CsCl MgBr2 Al2S3

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Review I

Naming Binary Ionic Compounds for Metals with Variable Charge
• • contain metal cation + nonmetal anion metal listed first in formula and name

1. Name metal cation first, name nonmetal anion second. 2. Metal cation name is metal name followed by a Roman numeral in parentheses to indicate its…