Chemical Bonding and Nomenclature

1
Chemical Bonding and Nomenclature

• Chapter 5

2
What is a Molecule ?

• Molecule
• A collection of atoms bonded together
• Elemental molecules
• Atoms from same element
• Diatomic H2, N2, O2, F2, I2, Br2
• Polyatomic P4, S8

3
What is a Molecule

• Molecules of Compounds
• Atoms of different elements
• Simple vs. Complicated
• Small vs. extremely large

4
Properties of Molecules

• Molecules have different properties than their
  elemental component.

Element Properties
O Odorless, colorless very reactive toxic gas
H Odorless colorless gas reactive
5
Properties of Molecules
Molecule Properties
O2 Colorless odorless gas moderately reactive not flammable
H2 Colorless odorless gas moderately reactive flammable
H2O Colorless odorless liquid, low reactivity
H2O2 Colorless odorless liquid high reactivity
6
Why do molecules form?

• To be like the noble gases
• The noble gases are perfect hence they do not
  react with anything
• They have 8 valence electrons in their outer most
  shell

7
Valence Electrons?

• The outermost electrons. Determines the chemical
  properties of an element
• The only electrons that bond
• The roman numerals at the top of each group A
  element
• Most elements prefer to have 8 electrons this is
  called the octet rule. Why?

8
The Octet Rule

• Atoms tend to gain, lose, or share electrons
  until they have eight valence electrons.

9
Electron Dot diagrams

• A way of keeping track of valence electrons.
• How to write them
• Write the symbol.
• Put one dot for each valence electron
• Dont pair up until you have too.

X
10
The Electron Dot diagram for Nitrogen

• Nitrogen has 5 valence electrons.
• First we write the symbol.

N

• Then add 1 electron at a time to each side.

• Until they are forced to pair up.

11
Write the electron dot diagram for

• Na
• Mg
• C
• O
• F
• Al
• He

12
Electron Configurations for Cations

• Metals lose electrons to attain noble gas
  configuration.
• They make positive ions.

13
Electron Dots For Cations

• Metals will have few valence electrons

Ca
14
Electron Dots For Cations

• Metals will have few valence electrons
• These will come off

Ca
15
Electron Dots For Cations

• Metals will have few valence electrons
• These will come off
• Forming positive ions

Ca2
16
Electron Configurations for Anions

• Nonmetals gain electrons to attain noble gas
  configuration.
• They make negative ions.

17
Electron Dots For Anions

• Nonmetals will have many valence .electrons.
• They will gain electrons to fill outer shell.

P
P-3
18
Stable Electron Configurations

• All atoms react to achieve noble gas
  configuration.
• Noble gases 8 valence electrons .
• Also called the octet rule.

Ar
19
Covalent Bonding
20
How does H2 form?

• The nuclei repel

21
How does H2 form?

• The nuclei repel
• But they are attracted to electrons
• They share the electrons

22
Covalent bonds

• Nonmetals hold onto their valence electrons.
• They cant give away electrons to bond.
• Still want noble gas configuration.
• Get it by sharing valence electrons with each
  other.
• By sharing both atoms get to count the electrons
  toward noble gas configuration.

23
Covalent bonding

• Fluorine has seven valence electrons

24
Covalent bonding

• Fluorine has seven valence electrons
• A second atom also has seven

25
Covalent bonding

• Fluorine has seven valence electrons
• A second atom also has seven
• By sharing electrons

26
Single Covalent Bond

• A sharing of two valence electrons.
• Only nonmetals and Hydrogen.

27
How to show how they formed

• Its like a jigsaw puzzle.
• I have to tell you what the final formula is.
• You put the pieces together to end up with the
  right formula.
• For example- show how water is formed with
  covalent bonds.

28
Water
Each hydrogen has 1 valence electron Each
hydrogen wants 1 more The oxygen has 6 valence
electrons The oxygen wants 2 more They share to
make each other happy
29
Water

• Put the pieces together
• The first hydrogen is happy
• The oxygen still wants one more

H
30
Water

• The second hydrogen attaches
• Every atom has full energy levels

H
H
31
Multiple Bonds

• Sometimes atoms share more than one pair of
  valence electrons.
• A double bond is when atoms share two pair (4) of
  electrons.
• A triple bond is when atoms share three pair (6)
  of electrons.

32
Carbon dioxide

• CO2 - Carbon is central atom ( I have to tell
  you)
• Carbon has 4 valence electrons
• Wants 4 more
• Oxygen has 6 valence electrons
• Wants 2 more

C
33
Carbon dioxide

• Attaching 1 oxygen leaves the oxygen 1 short and
  the carbon 3 short

C
34
Carbon dioxide

• Attaching the second oxygen leaves both oxygen 1
  short and the carbon 2 short

C
35
Carbon dioxide

• The only solution is to share more

C
36
Carbon dioxide

• The only solution is to share more

C
37
Carbon dioxide

• The only solution is to share more

C
O
38
Carbon dioxide

• The only solution is to share more

C
O
39
Carbon dioxide

• The only solution is to share more

C
O
40
Carbon dioxide

• The only solution is to share more

C
O
O
41
Carbon dioxide

• The only solution is to share more
• Requires two double bonds
• Each atom gets to count all the atoms in the bond

C
O
O
42
Carbon dioxide

• The only solution is to share more
• Requires two double bonds
• Each atom gets to count all the atoms in the bond

8 valence electrons
C
O
O
43
Carbon dioxide

• The only solution is to share more
• Requires two double bonds
• Each atom gets to count all the atoms in the bond

8 valence electrons
C
O
O
44
Carbon dioxide

• The only solution is to share more
• Requires two double bonds
• Each atom gets to count all the atoms in the bond

8 valence electrons
C
O
O
45
A. Octet Rule

• Exceptions

• Hydrogen ? 2 valence e-

• Groups 1,2,3 get 2,4,6 valence e-

• Expanded octet ? more than 8 valence e- (e.g. S,
  P, Xe)

• Radicals ? odd of valence e-

46
B. Drawing Lewis Diagrams

• Find total of valence e-.
• Arrange atoms - singular atom is usually in the
  middle.
• Form bonds between atoms (2 e-).
• Distribute remaining e- to give each atom an
  octet (recall exceptions).
• If there arent enough e- to go around, form
  double or triple bonds.

47
B. Drawing Lewis Diagrams

• CF4

1 C 4e- 4e- 4 F 7e- 28e- 32e-
F F C F F
- 8e- 24e-
48
B. Drawing Lewis Diagrams

• BeCl2

1 Be 2e- 2e- 2 Cl 7e- 14e- 16e-
Cl Be Cl
- 4e- 12e-
49
B. Drawing Lewis Diagrams

• CO2

1 C 4e- 4e- 2 O 6e- 12e- 16e-
O C O
- 4e- 12e-
50
C. Polyatomic Ions

• To find total of valence e-
• Add 1e- for each negative charge.
• Subtract 1e- for each positive charge.
• Place brackets around the ion and label the
  charge.

51
C. Polyatomic Ions

• ClO4-

1 Cl 7e- 7e- 4 O 6e- 24e- 31e-
O O Cl O O
1e- 32e-
- 8e- 24e-
52
C. Polyatomic Ions

• NH4

1 N 5e- 5e- 4 H 1e- 4e- 9e-
H H N H H
- 1e- 8e-
- 8e- 0e-
53
D. Resonance Structures

• Molecules that cant be correctly represented by
  a single Lewis diagram.
• Actual structure is an average of all the
  possibilities.
• Show possible structures separated by a
  double-headed arrow.

54
D. Resonance Structures

• SO3

55
Practice

• Complete the worksheet

56
Nomenclature-Naming Chemical Compounds
57
Atoms and ions

• Atoms are electrically neutral.
• Same number of protons and electrons.
• Ions are atoms, or groups of atoms, with a
  charge.

58
Atoms and Ions

• Different numbers of protons and electrons.
• Only electrons can move.
• Gain or lose electrons.

59
Anion

• A negative ion.
• Has gained electrons.
• Non metals can gain electrons.
• Charge is written as a super script on the right.

F-1
Has gained one electron
O-2
Has gained two electrons
60
Cations

• Positive ions.
• Formed by losing electrons.
• More protons than electrons.
• Metals form cations.

K1
Has lost one electron
Ca2
Has lost two electrons
61
Two Types of Compounds

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

62
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.

63
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.

64
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
65
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

66
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.
• Elements in the same group have similar
  properties.
• Including the charge when they are ions.

67
1
2
3
-3
-2
-1
68
Naming ions

• We will use the systematic way.
• 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.

69
Name these

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

70
Write Formulas for these

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

71
Naming Anions

• Anions are always the same.
• Change the element ending to ide
• F-1 Fluoride

72
Name these

• Cl-1
• N-3
• Br-1
• O-2

73
Write these

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

74
Polyatomic ions

• Groups of atoms that stay together and have a
  charge.
• Acetate C2H3O2-1
• Nitrate NO3-1
• Nitrite NO2-1
• Hydroxide OH-1
• Permanganate MnO4-1
• Cyanide CN-1

75
Polyatomic ions

• Sulfate SO4-2
• Sulfite SO3-2
• Carbonate CO3-2
• Chromate CrO4-2
• Dichromate Cr2O7-2

• Phosphate PO4-3
• Phosphite PO3-3
• Ammonium NH41

76
Ions and Ionic Compounds
77
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.
• Group A
• NaCl Na Cl- sodium chloride
• MgBr2 Mg2 Br- magnesium bromide

78
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.

79
Naming Binary Ionic Compounds

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

80
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
• Fe must be 3
• iron (III) oxide

81
Naming Binary Ionic Compounds

• Write the names of the following
• KCl
• Na3N
• CrN
• Na2Se

82
Ternary Ionic Compounds

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

83
Ternary Ionic Compounds

• LiCN
• Fe(OH)3
• (NH4)2CO3
• NiPO4

84
Writing Formulas

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

85
Writing Formulas

• Write the formula for calcium chloride.
• Calcium is Ca2
• Chloride is Cl-1
• Ca2 Cl-1
• CaCl2

86
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

87
Write the formulas for these

• Ammonium chloride
• ammonium sulfide
• barium nitrate

88
Things to look for

• If cations have (), the number 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

89
Molecular Compounds
90
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

91
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

92
Prefixes

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

93
Prefixes

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

94
Name These

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

95
Write formulas for these

• diphosphorus pentoxide
• tetraiodide nonoxide
• sulfur hexaflouride
• nitrogen trioxide
• Carbon tetrahydride
• phosphorus trifluoride
• aluminum chloride

96
Naming Acidsa little tricky so pay attention
97
Acids

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

98
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

99
Naming Acids

• If the anion has oxygen in it
• it ends in -ate or -ite
• change the suffix -ate to -ic acid
• HNO3 Hydrogen and nitrate ions
• Nitric acid
• change the suffix -ite to -ous acid
• HNO2 Hydrogen and nitrite ions
• Nitrous acid

100
Name these

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

101
Writing 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

102
Write formulas for these

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