Hybrid orbitals, Lewis
diagrams, the octet rule
Gilbert
Newton
Lewis
(surrounded
by pairs of
electrons)
Review
• We can visualize a covalent bond as a
balance between attraction and repulsion
• A second way to view the formation of a
bond is to consider orbital diagrams
• Video (15 min - stop at HCl)
• Now we can visualize atoms bonding
because of the lower energy achieved via
the stability of filled valence shells
• The bottom line: atoms gain, lose, or share
electrons to obtain noble gas electron
configurations
Video: filling subshells
Video: filling subshells
•Draw orbital diagrams for F + F, H + O, Li + F
Overlapping orbitals
• Draw orbital diagrams for F + F, H + O, Li + F
1s
2s
2p
2p
F2
2s
1s
1s
1s
2s
H2 O
2p
1s
1s
2s
2p
2s
1s
LiF is ionic (metal + non-metal)
Hybrid orbitals
• Two overlapping orbitals form what is known
as a hybrid or molecular orbital
• Just as in a s,p,d, or f orbital the electrons
can be anywhere in the orbital (even though
the electron has started out in one atom, at
times, it may be closer to the other nucleus)
• Each hybrid orbital has a specific shape
(described in chapter 8)
• You do not need to know shapes
• You need to know that hybrid orbitals exist
and that they are formed from overlapping
orbitals
Lewis diagrams
• Read Pg. 229. Draw Lewis dot diagrams for
Ne, Sb, Rb, F. How many variations of the
Lewis diagram for P can be drawn?
Ne
P
Sb
P
Rb
P
F
P
• Lewis diagrams follow the octet rule: atoms
when forming ions, or bonding to other atoms
in compounds have 8 outer electrons
• Q - How can the octet rule be explained?
• A - s (2 e–) and p (6 e–) orbitals are filled
Ionic bonding
• Recall: Ionic bonding involves 3 steps:
1) loss of e-, 2) gain of e-, 3) +ve, -ve attract
–
e
1)
2)
Na
Cl
3)
Na+
Na+
Cl–
This can be represented via Lewis diagrams…
• Read remainder of 7.2 (pg. 230)
• Diagram the reaction between Li + Cl and
Mg + O (PE 3)
The octet rule (ionic compounds)
• Draw Li + Cl and Mg + O (PE 3, pg. 230)
Li
Cl
Mg
O
[Li]+ [ Cl ]–
[Mg]2+ [
O
]2–
• Note also that the charge on an ion can be
determined by the number of places
removed from a noble gas (Ca, N, Al?)
• Ca2+, N3-, Al3+
• See pg. 230 for example of Ca + Cl
Covalent bonding
• Covalent bonds can also be shown via Lewis
diagrams - E.g draw Lewis diagrams showing
the combination of 1) H+Cl, 2) C+Cl, 3) H+O,
4) Mg+F, 5) N+H, 6) Do PE 4 (pg. 234)
Cl
H Cl
HCl
Cl C Cl
Cl
CCl4
H O H
H 2O
[Mg]2+[
F
H N H
H
]2–
NH3
MgF2 - Ionic
• Note bonds can also be drawn with a dash to
represent two electrons (read 234-5 upto 7.5)
The octet rule (covalent compounds)
• (Read 7.4 up to PE4 (pg. 232 - 4). Do PE4.)
• Read remainder of 7.4
• Although the octet rule works for most
compounds, PCl5 and SF6 are examples of
exceptions (see pg. 235 for structures)
• Also, it can be difficult to draw the correct
bonds for atoms with multiple bonds
• Some clear rules have been established for
drawing Lewis structures
• We will see that the rules dictate molecular
structure, which dictates shape, which can
influence chemical properties of a compound
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