1. CHAPTER 7 CHEMICAL FORMULAS AND BONDING Date _____________
covalent bonding / Lewis diagrams
ionic _________________________________
the metal atom(s) _______________ enough ______________
to the nonmetal atom(s)
so that each resulting __________ has a _______________
the resulting ____________ and _____________ attract
covalent ______________________________
enough atoms _____________ enough __________________
so that each atom ends up with ___________________________
somehow ___________________________
holds atoms together…..
but electrons are all __________________
they __________________
how can they “glue” atoms together …!!! ???
metal plus nonmetal
transfer
electrons e-
ion
FOS
cation
anion - +
nonmetal plus nonmetal
share
electrons
the equivalent of a FOS
sharing electrons e-
negative
REPEL e-

2. BUT 1s 1 p+ p+ e- e- p+ p+ e- e-
covalent bonding ___________________________
use H2 as an example… 1H _____
electrons shared
oo ooo oooo
look at that
dudette over
there…
1s 1
a hydrogen atom
alone in the cosmos…
another hydrogen atom
alone in the cosmos…
attract p+ p+ e- e-
attract
attract
attractions pull
the atoms closer…
BUT
repulsions push
the atoms apart…
attract p+ p+ e- e-
repel
attract
attract
repel

3. p+ p+ e- e- covalent bonding ___________________________
electrons shared
attractions pull
the atoms closer…
BUT
repulsions push
the atoms apart…
attract p+ p+ e- e-
repel
attract
attract
repel
there will be a position (distance) where
______________________________________
the orbitals _______________________
attractions and repulsions balance
overlap

4. nuclei preferentially attracted to the “overlap”
covalent bonding ___________________________
electrons shared
attractions pull
the atoms closer…
BUT
repulsions push
the atoms apart… p+ p+ e- e-
nuclei preferentially
attracted to the
“overlap”
there will be a position (distance) where
______________________________________
the orbitals _______________________
orbital represents ___________________________
overlap = ___________________________________
___________________________________________
(that’s the bond)
attractions and repulsions balance
overlap
probability of where electrons can be
increased probability
electrons more likely to be BETWEEN the nuclei

5. nuclei preferentially attracted to the “overlap”
covalent bonding ___________________________
electrons shared
attractions pull
the atoms closer…
BUT
repulsions push
the atoms apart… p+ p+ e- e-
nuclei preferentially
attracted to the
“overlap”
the electrons are now shared in a new space….
a new _________________
that belongs to both atoms
how many electrons per orbital ? _______________
so each covalent bond is made up of _______ shared electrons
(that’s the glue)
orbital
TWO
TWO

6. Lewis structures (electron dot diagrams of formula units, molecules,
and polyatomic ions)
saw examples for ionic….
for covalent…
shows distribution of _________ electrons and how they are _________ so that each atom achieves the equivalent of a _________
electrons are shared in ______ 1 shared pair = _________
does NOT deal with how bonds are formed
does allow one to deduce the _______________________________
equivalent of a FOS ______________________________
(something about ______________)
comes from… if outer shell of a single atom is full,
the outer s- and p- sublevels are ___________
holding a total of _________________
this leads to a strong driving force for an atom to “have”
an octet of electrons in a molecule by achieved by sharing
valence
shared
FOS
pairs
one covalent bond
two atoms can share ___________________________
______________________________
1 pair = single bond
2 pairs = double bond
3 pairs = triple bond
3D structure (structure  properties)
 “octet” rule
eight
full
eight electrons

7. Rules for Lewis Structures
(for covalent structures… molecules and polyatomic ions)
Draw a skeleton (a frame)
Count valence electrons – total for all atoms
place the least electronegative atom in the middle (central atom)
EXCEPT for Hydrogen (of course!)… only has 1e to share…
so can only make one bond…. so can’t go in the middle
place the remaining atoms in some symmetrical pattern around the central atom

8. Place the valence electrons into the structure…b. c.
2 electrons between each bonding pair of atoms
place valence electrons in pairs around the outside atoms
to achieve an octet
EXCEPT for Hydrogen… only wants a “duet”
place any remaining valence electrons (in pairs) on the central atom
as nonbonding pairs (not shared)
** at this point, the central atom may have more than an octet

9. At this point, if the central atom has LESS than an octet…
use nonbonding pairs of electrons from the outside atoms
to make double / triple bonds with the central atom
(the non-bonding electrons now become shared)
A few points….
central atom ___________________________________
outside atom ___________________________________
for diatomics ___________________________________
_______________________________________
an atom bonded to more than one other atom
an atom bonded to one other atom
arbitrarily choose one of the atoms as the central atom
and then follow the rules
(but remember… there is no central atom)