Unit 4 Formulas and Naming

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Unit 4Formulas and Naming
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Writing Formulas and Naming Compounds

• Atoms and molecules react with one another to
  become more stable.
• Atoms become more stable by either gaining/losing
  electrons so that they have 8 valence electrons
  (full outer energy level).
• Na 1s2 2s2 2p6 3s1 1 valence electron
• Cl 1s2 2s2 2p6 3s2 3p5 7 valence electrons

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• Sodium will lose 1 e- to get 8 valence electrons
  (a noble gas configuration).
• Na ? Na1 1e-
• Chlorine will gain 1e- to get 8 valence e- (a
  noble gas configuration).
• Cl 1e- ? Cl-1
• Na1 and Cl-1 will combine to
• form a neutral molecule of NaCl
• Na1 Cl-1 ? NaCl

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Forming Ions

• Atoms form ions by gaining or losing electrons.
• metals tend to lose electrons (positive ions)
• Positive ions are also called cations
• nonmetals tend to gain electrons (negative ions)
• Negative ions are also called anions
• The position of the element on the periodic table
  can help determine how many valence electrons the
  atom has, and what charge it will probably have
  when it becomes an ion.

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Groups and Ion Charges
Group Valence e- Gain/Lose e- Ion charge
1 1 Lose 1 1
2 2 Lose 2 2
13 3 Lose 3 3
14 4 Tweener 4/-4
15 5 Gain 3 -3
16 6 Gain 2 -2
17 7 Gain 1 -1
18 8 0 0
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Monatomic Ions an ion made up of only one type
of atom (H1, Ca2, S-2, Cl-1, ) Polyatomic
Ions an ion made up of two or more different
types of atoms (NO3-1, OH-1, SO4-2, NH41,
) The compound Na3PO4 is made up of 3 monatomic
ions (Na1) and 1 polyatomic ion (PO4-3).
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Naming Monatomic Ions

• Ions are named differently than elements because
  they have different properties.
• In general
• Metals the word ion is added after the name of
  the element.
• Na sodium Na1 sodium ion
• Nonmetals the ending of the element is dropped,
  and ide is added.
• Br bromine Br-1 bromide
• O oxygen O-2 oxide

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Polyatomic Ions
Formula Name
NH41 Ammonium
NO3-1 Nitrate
ClO3-1 Chlorate
OH-1 Hydroxide
C2H3O2-1 Acetate
SO4-2 Sulfate
CO3-2 Carbonate
PO4-3 Phosphate
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Elements with more than one charge
Name Symbol Name Symbol
Copper (I) Cu1 Copper (II) Cu2
Chromium (II) Cr2 Chromium (III) Cr3
Manganese (II) Mn2 Manganese (III) Mn3
Cobalt (II) Co2 Cobalt (III) Co3
Iron (II) Fe2 Iron (III) Fe3
Nickel (II) Ni2 Nickel (III) Ni3
Tin (II) Sn2 Tin (IV) Sn4
Lead (II) Pb2 Lead (IV) Pb4
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Ionic Bond

• Formed from an attraction between oppositely
  charged ions
• Electrons are transferred from one atom to the
  other
• Formed between a metal and a non-metal

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Ionic Compounds

• made from ions combining
• have zero net charge (neutral)
• Even though it is made up of positive and
  negative ions
• to successfully write and name compounds
• must know names of ions
• must know charges of ions
• must know formulas of ions

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Naming Ionic Compounds

• Give the name of the positive ion, cation,
  including the roman numeral if appropriate
  followed by the name of the negative ion, anion.
• Names of the cation are the same as the name of
  the element.
• Names of monatomic anions usually end with -ide.
• Names of polyatomic anions usually end with ate.

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Practice Naming

• sodium chloride
• lithium nitrate
• copper (I) chloride
• copper (II) chloride
• strontium chlorate
• magnesium oxide
• calcium sulfate
• iron (III) bromide

• NaCl
• LiNO3
• CuCl
• CuCl2
• Sr(ClO3)2
• MgO
• CaSO4
• FeBr3

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Writing correct ionic formulas

• Write the cation followed by the anion
• Cross the numerical charges to become the
  subscripts. Drop all /- signs
• If the subscripts are 1, do not write the 1. If
  the subscripts are multiples, reduce them.
• If more than one polyatomic ion is needed, put (
  ) around the polyatomic ion before adding the
  subscript.

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Ionic Compounds

• Made up of positive and negative ions
• Made up of metals and nonmetals
• Salts
• Will conduct electricity when dissolved in water
• Electrons are transferred between atoms
• Opposites attract
• Positive ion always comes first

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Covalent Compounds

• Made up of two or more nonmetals
• Electrons are shared between atoms
• Do not conduct electricity in water
• No ions are present

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Prefixes
Prefix Meaning Prefix Meaning
Mono- 1 Hexa- 6
Di- 2 Hepta- 7
Tri- 3 Octa- 8
Tetra- 4 Nona- 9
Penta- 5 Deca- 10
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Naming covalent compounds

• Give the prefix telling how many of the first
  element (except mono-), then give the name of the
  first element.
• Give the prefix telling how many of the second
  element, then give the name of the second element
  ending with ide.
• P2O5 CO CO2 N2O4
• PCl3 ICl3 SiO2 N4Cl7

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How to name the compound

• If there is a metal and a nonmetal, name using
  the ion list.
• If there are two nonmetals, name using prefixes
  to tell how many of each element.

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How to write the correct formulas

• If it is ionic- write down the symbols and
  charges. Cross the charges and reduce.
• If it is covalent prefixes will tell how many
  of each element in the compound. DO NOT CROSS.