Chapter 9 Covalent Compounds

1
Chapter 9 Covalent Compounds
2
Covalent Compounds

• Ionic compounds are formed when one element has a
  stronger attraction to valence e- than another
  atom.
• If elements have similar attractions, they share
  electrons covalent bonding.

3
Covalent Compounds

• Covalent Bond
• The attraction of a nucleus on one atom with the
  valence electrons of another.
• results from sharing electrons
• two elements must have similar electronegativities
  
• generally formed between two nonmetals

4
Covalent BondingMolecules

• Molecule
• The structure formed when atoms bond covalently.
• Occurs when the bonded atoms are _____________ in
  energy than when the atoms are separate.

5
Covalent Compounds Lewis Structures

• Use Lewis Dot structures to show what molecule
  would be formed when the following atoms bond.

• H and F
• H and O
• N and H
• C and H

6
Covalent Compounds Lewis Structures

• Use Lewis Dot structures to show what molecule
  would be formed when the following atoms bond.

• O and O
• C and O
• N and N

??? ???
7
Covalent Compounds Bond Strength

• Bond Dissociation Energy
• Bond Energy
• The amount of energy required to ______ a
  specific bond.

8
Covalent Compounds Bond Strength

• Strength of Covalent Bonds
• 1) electron pairs shared
• Polarity (ionic character) of bonds
• size of atoms
• Note Bond length is an indicator of bond
  strength.
• The stronger the bond, the ___________ the bond.

9
Covalent Compounds Bond Strength

• Predict which bond is stronger in each of the
  following
• H2 or O2 or N2
• HF or HCl or HBr
• In the above examples, which bond is the longest?

10
Covalent Compounds Naming Binary Molecular
Compounds

• RULES - See Separate Sheet
• Use prefixes to indicate the number of atoms of
  each element. (omit mono- from first element)
• Name the first element using the correct prefix.
• 2) Name the second element by using the stem
  (and correct prefix) and adding the ending -ide
• CO carbon monoxide
• P2O5 diphosphorus pentoxide

11
Covalent Compounds Naming Binary Molecular
Compounds
Prefixes 1 mono 2 di 3 tri 4 tetra 5-
penta 6 hexa 7- hepta 8- octa 9 nona 10 - deca
12
Covalent Compounds Naming Binary Molecular
Compounds

• Practice
• N2O N2O5
• SF6 CCl4
• BF3 H2O

13
Covalent Compounds Naming Acids

• Naming Binary Acids
• Hydro(anion root)ic acid
• HF
• HCl
• HBr
• HI
• H2S

14
Covalent Compounds Naming Acids

• Naming Oxyacids

If the polyatomic ion contains -ate ? (root)ic
acid -ite ? (root)ous acid
H2SO4 H3PO4 HNO3
H2SO3 H3PO3 HNO2
NOTE Oxyacids do NOT use the prefix hydro-
15
Covalent Compounds Electronegativity and Polarity

• Electronegativity
• a measure of an atoms ability to attract the
  valence e- of another atom
• Electronegativity determines the type of bond
  thats formed
• (i.e. how the electrons are redistributed).

16
Covalent Compounds Electronegativity and Polarity

• Covalent Bonding Ionic Bonding

17
Covalent CompoundsProperties

• Properties
• _______ m.p./b.p.
• (many _________ at room temp.)
• _______ as solids
• Solubility in water?
• KEY Properties are due to type of bonding.

18
Ionic/Covalent - Review
19
Covalent Compounds Molecular Polarity

• Molecular polarity deals with whether or not the
  entire molecule is polar
• i.e. has partially (-) and () ends
• To have a polar molecule you need
• Polar bonds
• A geometry that doesnt cancel

20
Covalent CompoundsMolecular Polarity

• Which of the following compounds do you think are
  polar?