Transcript I. Why Atoms Combine - Manchester High School

Chemical Bonds
I. Why Atoms Combine
 Chemical Formula
 Chemical Bond
 Stability
A. Chemical Formula
 Shows:
1) elements in the compound
2) ratio of their atoms
H2O
1 oxygen atom
2 hydrogen atoms
B. Chemical Bond
 Strong attractive force between atoms
or ions in a molecule or compound.
 Formed by:
• transferring e- (losing or gaining)
• sharing e-
C. Stability
 Octet Rule
• most atoms form bonds in order to
have 8 valence e• full outer energy level
Ne
• like the Noble Gases!
 Stability is the driving force behind bond
formation!
C. Stability
 Transferring e-
 Sharing e-
Chemical Bonds
II. Kinds of Chemical Bonds
 Ionic Bond
 Covalent Bond
 Comparison Chart
A. Ionic Bond
 Attraction between 2 oppositely
charged ions
• Ions - charged atoms
• formed by
transferring efrom a metal
to a nonmetal
A. Ionic Bond
• ions form a 3-D crystal lattice
NaCl
B. Covalent Bond
 Attraction between neutral atoms
• formed by sharing e- between two
nonmetals
B. Covalent Bond
• covalent bonds result in discrete
molecules
Cl2
NH3
H2O
Covalent Bond –sharing
B. Covalent Bond
 Nonpolar Covalent Bond
• e- are shared equally
• usually identical atoms
B. Covalent Bond
 Polar Covalent Bond
• e- are shared unequally between 2
different atoms
• results in partial opposite charges
+


B. Covalent Bond
 Nonpolar
 Polar
 Ionic
View Bonding Animations.
C. Comparison Chart
IONIC
transferred from
metal to nonmetal
COVALENT
shared between
nonmetals
Melting
Point
high
low
Soluble in
Water
yes
usually not
Electrons
Conduct
Electricity
Other
Properties
yes
no
(solution or liquid)
crystal lattice of ions, molecules, odorous
liquids & gases
crystalline solids
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Chemical Bonds
III. Naming Molecular
Compounds
 Molecular Names
 Molecular Formulas
A. Molecular Names
 Write the names of both elements.
 Change the final ending to -ide.
 Add prefixes to indicate subscripts.
 Only use mono- prefix with oxide.
A. Molecular Names
PREFIX
monoditritetrapentahexa-
SUBSCRIPT
1
2
3
4
5
6
A. Molecular Names
 CCl4
• carbon tetrachloride
 N2O
• dinitrogen monoxide
 SF6
• sulfur hexafluoride
B. Molecular Formulas
 Write the more metallic element first.
 Add subscripts according to prefixes.
B. Molecular Formulas
 phosphorus trichloride
• PCl3
 dinitrogen pentoxide
• N2O5
 dihydrogen monoxide
• H2O
B. Molecular Formulas
 The Seven Diatomic Elements
Br2 I2 N2 Cl2 H2 O2 F2
Chemical Bonds
IV. Naming Ionic Compounds
 Oxidation Number
 Ionic Names
 Ionic Formulas
A. Oxidation Number
 The charge on an ion.
 Indicates the # of e- gained/lost to
become stable.
1+
2+
0
3+ 4+ 3- 2- 1-
B. Ionic Names
 Write the names of both elements, cation
first.
 Change the anion’s ending to -ide.
 Write the names of polyatomic ions.
 For ions with variable oxidation #’s, write
the ox. # in parentheses using Roman
numerals. Overall charge = 0. (Transition
metals)
B. Ionic Names
 NaBr
• sodium bromide
 Na2CO3
• sodium carbonate
 FeCl3
• iron(III) chloride
C. Ionic Formulas
 Write each ion. Put the cation first.
 Overall charge must equal zero.
• If charges cancel, just write the symbols.
• If not, crisscross the charges to find
subscripts.
 Use parentheses when more than one
polyatomic ion is needed.
 Roman numerals indicate the oxidation #.
C. Ionic Formulas
 potassium chloride
• K+ Cl-

KCl
 magnesium nitrate
• Mg2+ NO3-

Mg(NO3)2
 copper(II) chloride
• Cu2+ Cl-

CuCl2
C. Ionic Formulas
 calcium oxide
• Ca2+ O2-

CaO
 aluminum chlorate
• Al3+ ClO3- 
Al(ClO3)3
 iron(III) oxide
• Fe3+ O2-

Fe2O3
Covalent Bond Naming
 SiO2
silicon dioxide
 NO
nitrogen monoxide
 XeF4
Xenon tetrafluoride
Covalent Bond Naming
 P4S3
Tetraphosphorus trisulfide
 PBr3
phosphorus tribromide
 CS2
carbon disulfide
Covalent bond formula
 Nitrogen trifluoride
NF3
Dinitrogen pentoxide
N2O5
Covalent Bond formula
Trisilicon tetranitride
Si3N4
Carbon dioxide
CO2