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Chapter 9:
Chemical Bonds
Chemical Terminology
• Atom
• Molecule
Chemical Reactions
• Formation and/or breaking
of chemical bonds
• Chemical energy
• Chemical equation
Fig 9.4
Valence Electrons and Ions
• Outer orbital electrons
participate in bonding
• A-Group (family) number
and electron dot notation
• Octet rule
Fig 9.5
Chemical Bonds
• Attractive forces holding atoms
together in compounds
Three types of bonds:
• Metallic
• Ionic
• Covalent
Ionic Bonds
• Chemical bond of
electrostatic attraction
• Example: NaCl
– Na loses; Cl gains
– No single NaCl molecule,
per se.
Common Ions
and Polyatomic Ions
Covalent Bonds
Fig 9.8
Covalent Bonds
• Covalent compound
• Electron dot representation
Multiple Covalent Bonds
• Sharing of more than
one electron pair
• Examples
– Ethylene: Double bond
– Acetylene: Triple bond.
Bond Polarity
• Polar Covalent Bonds
• Electronegativity
Electronegativities
Fig 9.10
Composition of Compounds
• Common names
• Modern approach - systematic sets of rules
Ionic Compounds and
Formulas
Ionic Compound Names
• Name of metal (positive) ion first;
then non-metal (negative) ion
• If no polyatomic ions are involved,
the suffix –ide is added to the end of
the non-metal
• Many elements have variable charges
– Historical suffix usage
• “-ic” and “-ous”
– Modern approach
• English name of metal followed by
Roman numeral indicating charge.
Ionic Compound Formulas
• Two Rules
– Write symbol for positive ion first followed by
the symbol for the negative ion
– Assign subscripts to assure compound is
electrically neutral using cross-over technique
• Example:
Calcium chloride.
Covalent Compounds
(AKA Molecules)
• Held together by covalent bonds
– Composed of two or more non-metals
– Number of bonds determined by “valence”
• Can be different elements or same elements
– Carbon Tetrachloride (CCl4) ; Oxygen gas (O2)
Covalent Compound Names
Two rules
• First element in formula named first with number
indicated by Greek prefix
• Stem name of second element next; Greek prefix
for number; ending in “-ide” if only two elements
are involved.
Covalent Compound Formulas
• Examples: carbon dioxide,
carbon tetrachloride
• Valence
– Number of covalent bonds
an atom can form
– Hydrogen valence is 1 ;
can only form single
bonds
– Oxygen is 2; single and
double bonds
– Nitrogen is 3; single,
double and triple bonds
– Carbon is 4 - single,
double and triple bonds.
Next:
Chemical Reactions