Chapter 6 Chemical Names and Formulas

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Chapter 6Chemical Names and Formulas

• Charles Page High School
• Dr. Stephen L. Cotton

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Section 6.1Introduction to Chemical Bonding

• OBJECTIVES
• Distinguish between ionic and molecular compounds.

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Section 6.1Introduction to Chemical Bonding

• OBJECTIVES
• Define cation and anion, and relate them to metal
  and nonmetal.

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Molecules and Molecular Compounds

• About 100 different elements
• Millions of compounds from them
• Naming is essential in chemistry
• Noble gases, such as He and Ne
• Isolated atoms- monatomic, they consist of single
  atoms

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Molecules and Molecular Compounds

• Molecule- smallest electrically neutral unit,
  still has properties of the substance
• Made from only nonmetals
• Can be from one element- O2
• Can make a compound- CO2

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Molecules and Molecular Compounds

• Properties of molecular compounds
• Low melting and boiling points
• Usually gas or liquid
• Composed of two or more nonmetals
• O2, O3, H2O

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Systematic Naming

• There are too many compounds to remember the
  names of them all.
• Compound is made of two or more elements.
• Put together atoms.
• Name should tell us how many and what type of
  atoms.

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Atoms and ions

• Atoms are electrically neutral.
• Same number of protons and electrons.
• Ions are atoms, or groups of atoms, with a charge
  (positive or negative)
• Different numbers of protons and electrons.
• Only electrons can move.
• Gain or lose electrons.

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Anion

• A negative ion.
• Has gained electrons.
• Nonmetals can gain electrons.
• Charge is written as a superscript on the right.

Has gained one electron (-ide is new ending
fluoride)
F1-
O2-
Gained two electrons (oxide)
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Cations

• Positive ions.
• Formed by losing electrons.
• More protons than electrons.
• Metals can lose electrons

Has lost one electron (no name change for
positive ions)
K1
Ca2
Has lost two electrons
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Ionic Compounds

• Ionic compounds- from joining metal cations and
  nonmetal anions- they are electrically neutral
• Usually solid crystals
• Melt at high temperatures

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Two Types of Compounds

• Molecular compounds
• Made of molecules.
• Made by joining nonmetal atoms together into
  molecules.

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Two Types of Compounds

• Ionic Compounds
• Made of cations and anions.
• Metals and nonmetals.
• The electrons lost by the cation are gained by
  the anion.
• The cation and anions surround each other.
• Smallest piece is a FORMULA UNIT.

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Two Types of Compounds
Ionic
Molecular
Smallest piece
Formula Unit
Molecule
Types of elements
Metal and Nonmetal
Nonmetals
Solid, liquid or gas
State
solid
Melting Point
High gt300ºC
Low lt300ºC
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Section 6.2Representing Chemical Compounds

• OBJECTIVES
• Distinguish among chemical formulas, molecular
  formulas, and formula units.

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Section 6.2Representing Chemical Compounds

• OBJECTIVES
• Use experimental data to show that a compound
  obeys the law of definite proportions.

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Chemical Formulas

• Shows the kind and number of atoms in the
  smallest piece of a substance.
• Molecular formula- number and kinds of atoms in a
  molecule.
• CO2
• C6H12O6

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Chemical Formulas

• More than one atom? use a subscript (H2O)
• There are 7 diatomic elements
• Hydrogen (H2), Nitrogen (N2), Oxygen (O2),
  Fluorine (F2), Chlorine (Cl2), Bromine (Br2), and
  Iodine (I2)
• Remember Br I N Cl H O F

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Ionic Compounds

• This formula represents not a molecule, but a
  formula unit
• The smallest whole number ratio of atoms in an
  ionic compound.
• Ions surround each other so you cant say which
  is hooked to which. (p. 140)

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Some Laws

• 1. Law of Definite Proportions- in a sample of a
  chemical compound, the masses of the elements are
  always in the same proportions.
• H2O (water) and H2O2 (hydrogen peroxide)

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Some Laws

• 2. Law of Multiple Proportions- Dalton stated
  that whenever two elements form more than one
  compound, the different masses of one element
  that combine with the same mass of the other
  element are in the ratio of small whole numbers.
• Figure 6.11, p. 141

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Section 6.3Ionic Charges

• OBJECTIVES
• Use the periodic table to determine the charge on
  an ion.

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Section 6.3Ionic Charges

• OBJECTIVES
• Define a polyatomic ion, and give the names and
  formulas of the most common polyatomic ions.

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Charges on ions

• For most of the Group A elements, the Periodic
  Table can tell what kind of ion they will form
  from their location monatomic ions
• Elements in the same group have similar
  properties.
• Including the charge when they are ions.

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1
2
3
3-
2-
1-
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What about the others?

• Groups 4A and 0 do not usually form ions (in
  fact, Group 0 rarely forms compounds!)
• Many transition metals have more than one common
  ionic charge

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Naming ions

• Two methods if more than one charge is possible
• 1. Stock system uses roman numerals in
  parenthesis to indicate the numerical value
• 2. Classical method uses root word with
  suffixes (-ous, -ic)
• Does not give true value

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Naming ions

• We will use the Stock system.
• Cation- if the charge is always the same (Group
  A) just write the name of the metal.
• Transition metals can have more than one type of
  charge.
• Indicate the charge with roman numerals in
  parenthesis (Table 6.3, p.144)

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Name these

• Na1
• Ca2
• Al3
• Fe3
• Fe2
• Pb2
• Li1

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Write Formulas for these

• Potassium ion
• Magnesium ion
• Copper (II) ion
• Chromium (VI) ion
• Barium ion
• Mercury (II) ion

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Naming Anions

• Anions are always the same charge
• Change the element ending to ide
• F1- Fluorine

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Naming Anions

• Anions are always the same charge
• Change the element ending to ide
• F1- Fluorin

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Naming Anions

• Anions are always the same charge
• Change the element ending to ide
• F1- Fluori

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Naming Anions

• Anions are always the same charge
• Change the element ending to ide
• F1- Fluor

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Naming Anions

• Anions are always the same charge
• Change the element ending to ide
• F1- Fluori

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Naming Anions

• Anions are always the same charge
• Change the element ending to ide
• F1- Fluorid

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Naming Anions

• Anions are always the same charge
• Change the element ending to ide
• F1- Fluoride

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Name these

• Cl1-
• N3-
• Br1-
• O2-
• Ga3

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Write these

• Sulfide ion
• iodide ion
• phosphide ion
• Strontium ion

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Exceptions

• Some of the transition metals have only one ionic
  charge
• Do not use roman numerals for these
• Silver is always 1 (Ag1)
• Cadmium and Zinc are always 2 (Cd2 and Zn2)
• Note Fig. 6.13, p. 145

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Polyatomic ions

• Groups of atoms that stay together and have a
  charge.
• Learn these - Table 6.4, p.147
• Acetate C2H3O21-
• Nitrate NO31-
• Nitrite NO21-
• Hydroxide OH1- and Cyanide CN1-
• Permanganate MnO41-

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Polyatomic ions

• Sulfate SO42-
• Sulfite SO32-
• Carbonate CO32-
• Chromate CrO42-
• Dichromate Cr2O72-

• Phosphate PO43-
• Phosphite PO33-
• Ammonium NH41

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Section 6.4Ionic Compounds

• OBJECTIVES
• Apply the rules for naming and writing formulas
  for binary ionic compounds.

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Section 6.4Ionic Compounds

• OBJECTIVES
• Apply the rules for naming and writing formulas
  for ternary ionic compounds.

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Naming Binary Ionic Compounds

• Binary Compounds - 2 elements.
• Ionic - a cation and an anion.
• To write the names, just name the two ions.
• Easy with Representative elements (which are
  Group A elements)
• NaCl Na1 Cl1- sodium chloride
• MgBr2 Mg2 Br1- magnesium bromide

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Naming Binary Ionic Compounds

• The problem comes with the transition metals.
• Need to figure out their charges.
• The compound must be neutral.
• same number of and charges.
• Use the anion to determine the charge on the
  positive ion.

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Naming Binary Ionic Compounds

• Write the name of CuO
• Need the charge of Cu
• O is 2-
• copper must be 2
• Copper (II) oxide
• Name CoCl3
• Cl is 1- and there are three of them 3-
• Co must be 3 Cobalt (III) chloride

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Naming Binary Ionic Compounds

• Write the name of Cu2S.
• Since S is 2-, the Cu2 must be 2, so each one is
  1.
• copper (I) sulfide
• Fe2O3
• Each O is 2- 3 x -2 -6
• 2 Fe must 6, so each is 3.
• iron (III) oxide

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Naming Binary Ionic Compounds

• Write the names of the following
• KCl
• Na3N
• CrN
• Sc3P2
• PbO
• PbO2
• Na2Se

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Ternary Ionic Compounds

• These will have polyatomic ions
• At least three elements
• name the ions
• NaNO3
• CaSO4
• CuSO3
• (NH4)2O

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Ternary Ionic Compounds

• LiCN
• Fe(OH)3
• (NH4)2CO3
• NiPO4

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Writing Formulas

• The charges have to add up to zero.
• Get charges on pieces.
• Cations from name on table.
• Anions from table or polyatomic.
• Balance the charges by adding subscripts.
• Put polyatomics in parenthesis.

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Writing Formulas

• Write the formula for calcium chloride.
• Calcium is Ca2
• Chloride is Cl1-
• Ca2 Cl1- would have a 1 charge.
• Need another Cl1-
• Ca2 Cl21- (use criss-cross method)

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Write the formulas for these

• Lithium sulfide
• tin (II) oxide
• tin (IV) oxide
• Magnesium fluoride
• Copper (II) sulfate
• Iron (III) phosphide
• gallium nitrate
• Iron (III) sulfide

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Write the formulas for these

• Ammonium chloride
• ammonium sulfide
• barium nitrate

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Things to look for

• If cations have ( ), the number in parenthesis is
  their charge.
• If anions end in -ide they are probably off the
  periodic table (Monoatomic)
• If anion ends in -ate or -ite it is polyatomic

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Section 6.5Molecular Compounds and Acids

• OBJECTIVES
• Apply the rules for naming and writing formulas
  for binary molecular compounds.

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Section 6.5Molecular Compounds and Acids

• OBJECTIVES
• Name and write formulas for common acids.

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Molecular compounds

• made of just nonmetals
• smallest piece is a molecule
• cant be held together because of opposite
  charges.
• cant use charges to figure out how many of each
  atom

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Molecular are easier!

• Ionic compounds use charges to determine how many
  of each.
• Have to figure out charges.
• Have to figure out numbers.
• Molecular compounds name tells you the number of
  atoms.
• Uses prefixes to tell you the number

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Prefixes (Table 6.5, p.159)

• 1 mono-
• 2 di-
• 3 tri-
• 4 tetra-
• 5 penta-
• 6 hexa-
• 7 hepta-
• 8 octa-

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Prefixes

• 9 nona-
• 10 deca-
• To write the name, write two words

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Prefixes

• 9 nona-
• 10 deca-
• To write the name, write two words

Prefix
name
Prefix
name
-ide
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Prefixes

• 9 nona-
• 10 deca-
• To write the name, write two words
  
• One exception is we dont write mono- if there is
  only one of the first element.

Prefix
name
Prefix
name
-ide
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Prefixes

• 9 nona-
• 10 deca-
• To write the name, write two words
  
• One exception is we dont write mono- if there is
  only one of the first element.
• No double vowels when writing names (oa oo)

Prefix
name
Prefix
name
-ide
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Name These

• N2O
• NO2
• Cl2O7
• CBr4
• CO2
• BaCl2

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Write formulas for these

• diphosphorus pentoxide
• tetraiodine nonoxide
• sulfur hexafluoride
• nitrogen trioxide
• carbon tetrahydride
• phosphorus trifluoride
• aluminum chloride

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Acids

• Writing names and Formulas

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Acids

• Compounds that give off hydrogen ions when
  dissolved in water.
• Must have H in them.
• will always be some H next to an anion.
• The anion determines the name.

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Naming acids

• If the anion attached to hydrogen ends in -ide,
  put the prefix hydro- and change -ide to -ic acid
• HCl - hydrogen ion and chloride ion
• hydrochloric acid
• H2S hydrogen ion and sulfide ion
• hydrosulfuric acid

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Naming Acids

• If the anion has oxygen in it, then it ends in
  -ate of -ite
• change the suffix -ate to -ic acid (use no
  prefix)
• HNO3 Hydrogen and nitrate ions
• Nitric acid
• change the suffix -ite to -ous acid
• HNO2 Hydrogen and nitrite ions
• Nitrous acid

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Name these

• HF
• H3P
• H2SO4
• H2SO3
• HCN
• H2CrO4

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Writing Acid Formulas

• Hydrogen will always be first
• name will tell you the anion
• make the charges cancel out.
• Starts with hydro?- no oxygen, -ide
• no hydro?, -ate comes from -ic, -ite comes from
  -ous

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Write formulas for these

• hydroiodic acid
• acetic acid
• carbonic acid
• phosphorous acid
• hydrobromic acid

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Section 6.6Summary of Naming and Formula Writing

• OBJECTIVES
• Use the flowchart in Figure 6.21 to write the
  name of a compound when given its chemical
  formula.

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Section 6.6Summary of Naming and Formula Writing

• OBJECTIVES
• Use the flowchart in Figure 6.23 to write a
  chemical formula when given the name of a
  compound.

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Helpful to remember...

• 1. In an ionic compound, the net ionic charge is
  zero (criss-cross method)
• 2. An -ide ending generally indicates a binary
  compound
• 3. An -ite or -ate ending means there is a
  polyatomic ion that has oxygen
• 4. Prefixes generally mean molecular they show
  the number of each atom

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Helpful to remember...

• 5. A Roman numeral after the name of a cation
  shows the ionic charge of the cation
• Use the handout sheets provided by your teacher!

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Summary of Naming and Formula Writing

• For naming, follow the flowchart- Fig. 6.21, page
  161
• For writing formulas, follow the flowchart from
  Fig. 6.23, p. 162