Covalent bonding

1
Chapter 4

• Covalent bonding

2
How does H2O form?

• Oxygen has 6 valence electrons.
• Does Hydrogen give up its one electron?

3
How about H2?

• The nuclei repel because of positive charges
• But they are attracted to electrons
• They share the electrons

4
Covalent Bonds

• Formed by the attraction of two atoms for a
  shared pair of electrons.
• Neither atom will have a charge.
• Molecule - an uncharged group of two or more
  atoms held together by covalent bonds.

5
Covalent Bonds

• Do nonmetals gain or lose electrons to attain
  noble gas configuration?
• Can two or more nonmetals form a bond?

YES!
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How?

• BY SHARING ELECTRONS

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Covalent bonding

• Fluorine has seven valence electrons

8
Covalent bonding

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

9
Covalent bonding

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

10
Covalent bonding

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

11
Covalent bonding

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

12
Covalent bonding

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

13
Covalent bonding

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

14
Covalent bonding

• Fluorine has seven valence electrons
• A second atom also has seven
• By sharing electrons
• Both end with full orbitals

15
Covalent bonding

• Fluorine has seven valence electrons
• A second atom also has seven
• By sharing electrons
• Both end with full orbitals

F
F
8 Valence electrons
16
Covalent bonding

• Fluorine has seven valence electrons
• A second atom also has seven
• By sharing electrons
• Both end with full orbitals

F
F
8 Valence electrons
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Single Covalent Bond

• A sharing of two valence electrons.
• Occurs between nonmetals and Hydrogen.
• Form molecules, NOT ionic compounds.

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How to show how they formed

• Its like a jigsaw puzzle.
• I have to tell you what the final formula will
  be.
• You put the pieces together to end up with the
  right formula.

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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

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Water

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

H
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Water

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

H
H
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Multiple Covalent Bonds

• Atoms can share more than one pair of electrons
• - single covalent bonds (2 e-)
• - double covalent bonds (4e-)
• - triple covalent bonds (6e-)

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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
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Carbon dioxide

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

C
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Carbon dioxide

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

C
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Carbon dioxide

• The only solution is to share more

C
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Carbon dioxide

• The only solution is to share more

C
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Carbon dioxide

• The only solution is to share more

C
O
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Carbon dioxide

• The only solution is to share more

C
O
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Carbon dioxide

• The only solution is to share more

C
O
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Carbon dioxide

• The only solution is to share more

C
O
O
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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
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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
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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
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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
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How to draw them

• Add up all the valence electrons.
• This is the number you have to work with
• Use the guess and check method until all atoms
  have 8 electrons (except H and He)
• Some electrons will be shared

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Examples

• NH3 N is central
• N - has 5 valence electrons
• H - has 1 valence electrons

N
H
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Examples

• HCN C is central atom
• N - has 5 valence electrons
• C - has 4 valence electrons
• H - has 1 valence electrons
• Total of 10 electrons

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Another way of indicating bonds

• Often use a line to indicate a bond
• Called a structural formula
• Each line is 2 valence electrons

H
H
O
H
H
O
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Structural Examples

• C has 8 electrons because each line is 2
  electrons
• Ditto for N
• Ditto for C here
• Ditto for O

H C N
H
C O
H
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Interparticle Forces
42
Interparticle Forces

• Forces in molecular compounds are weaker than
  those in ionic compounds.

43
Molecular Compounds

• Usually not soluble in water
• Do not conduct electricity well (Why not?)
• Usually liquids or gases at room temperature