Bonding
Why do atoms bond?
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Atoms bond to get 8 valence electrons!
Octet Rule: atoms need 8 valence electrons to be
stable.
2 ways to get 8
1. transfer electrons (forms ions)
Ionic bonding
2. Share electrons Covalent bonding
Ionic Bonds (Review)
-Atoms lose or gain electrons to
become stable (like a noble gas)
-occurs between a metal and nonmetal
-occurs between a positive ion and
negative ion
Covalent Bonds
-Atoms share electrons to
become stable (like a noble gas)
-occurs between 2 non-metals
-covalent compounds are called
molecules
Which of the following are molecular and
which are ionic?
Molecular
Molecular
NaBr
Ionic
CO2 O3
Ionic
NO
KCl
Ionic
AlBr3
Ionic
Covalent Bonding
2 Types of Covalent Bonds
Nonpolar covalent- electrons are
shared equally
Polar Covalent- electrons shared
unequally
Naming and Writing
Formulas of
Covalent Compounds
Polar Bonds
-have a partial negative charge on the more
electronegative atom
-have a partial positive charge on the less
electronegative atom
Nomenclature
Since electrons are shared two elements can bond
in different ratios
Ex.:
CO Carbon monoxide
CO2 Carbon dioxide
We name covalent (molecular) compounds using
prefixes to indicate the number of atoms of each.
Prefixes
1 atom *mono- 6 atoms hexa2 atoms di7 atoms hepta3 atoms tri- 8 atoms octa4 atoms tetra- 9 atoms nona5 atoms penta- 10 atoms deca* Mono- is only used for the second element
Naming Molecular Compounds
Nomenclature:
1) Name the first element that appears in the formula.
2) Name the second element that appears in the formula,
changing its ending to –ide.
1. N2O4
* There are 2 nitrogen atoms and 4 oxygen atoms
Name: dinitrogen tetraoxide
2. NO
nitrogen monoxide
NO₂
As₂O5
PCl₃
CCl₄
Examples
Nitrogen dioxide
Diarsenic pentoxide
Phosphorous
trichloride
Carbon tetrachloride
Writing Formulas for Covalent
Compounds
-Prefixes tell you subscripts for elements!
Ex.:
1. Nitrogen trioxide
Nitrogen has no prefix so there is 1 atom of
nitrogen
The prefix tri- means there are 3 oxygens
Formula: NO3
Examples
H2 O
dihydrogen monoxide
sulfur hexafluoride
xenon trioxide
SF6
XeO3
tetraphosphorus trisulfide
P4 S3