Bonding class #2
OB: Metallic Bonds, More Lewis
Dots, and the Octet Rule.
When sodium chloride forms from sodium metal and chlorine non metal, the atoms
form ions first. To do this, the sodium TRANSFERS an electron to a chlorine atom .
The sodium becomes a sodium cation with a +1 charge
The chlorine becomes a chloride anion, with a -1 charge
Let’s draw the Lewis dot diagrams for the atoms, the ions, and then the compound.
ATOMS
IONS
COMPOUND
It’s important to note here, the sodium atom at 2-8-1 electron configuration becomes
2-8 as it loses one electron, becoming isoelectric to neon.
It loses enough electrons to get a perfect outer orbital, as defined by noble gases
having the most perfect, or most stable electron orbitals of all.
The chlorine atom has a 2-8-7 configuration, gains one electron, and becomes
2-8-8, making it isoelectric to argon.
Both ions end up with perfect outer orbitals, both end up isoelectric to a noble gas.
Both of these ions (all ions) will follow the octet rule: the octet rule is that
when bonding all ions will end up with eight outer most electrons, and when
bonding, all non-metals bonding together with other nonmetals in covalent
bonds, will end up with 8 electrons in the outermost orbitals.
This is a rule, but not a law. There are a few exceptions some ions are too small,
like Li, Some atoms can squeeze 10 electrons, we love exceptions!
Copy this table BIG, leave enough room for the dot diagrams!
Compound
name
Compound
Formula
Cation
Anion
Magnesium
oxide
MgO
Mg+2
O-2
LiF
CaCl2
Sodium…
S-2
Lewis Dot Diagram
Copy this table BIG, leave enough room for the dot diagrams!
Compound
name
Compound
Formula
Cation
Anion
Magnesium
oxide
MgO
Mg+2
O-2
Lithium
fluoride
LiF
Li+1
F-1
Calcium
chloride
CaCl2
Ca+2
Cl-1
Sodium…
Na2S
Na+1
S-2
Lewis Dot Diagram
Compound
name
Sodium…
Cesium
oxide
Compound
Formula
Cation
Anion
S-2
Lewis Dot Diagram
Compound
name
Compound
Formula
Cation
Anion
Sodium…
Na2S
Na+1
S-2
Cesium
oxide
Cs2O
Cs+1
O-2
Lewis Dot Diagram
Why is the formula for aluminum oxide Al2O3
and not some other ratio?
Each
metal
atom is
2-8-3
and
needs to
become
2-8
a +3
cation.
Follow
the octet
rule!
Al
O
O
Al
O
Each
nonmetal
atom is
2-6
and
needs to
become
2-8
a -2
anion.
Follow
the
octet
rule!
Why is the formula for aluminum oxide Al2O3
and not some other ratio?
Al
O
O
Al
O
A PERFECT TRANSFER OF ELECTRONS, 6 FROM Al + 6 INTO OXGYEN
Draw the UGLY Lewis dot diagram for Magnesium Nitride and also for Al2O3
This kind of bonding is to explain how metal atoms stick
together to form solid metals. Literally, how does about
6.02 x 1023 atoms of copper stick together so you can weigh
64 grams of copper on the scale?
For the same reason that these atoms can stick together,
nearly all of the properties of metals can be explained at
the same time.
As usual, it’s all about the electrons, where they are, what
they’re doing, and how fast they can move.
First, let’s name a few properties of metals…
Metals are
Malleable
Ductile
Conduct electricity
Form cations
etc.
These main properties can be explained by how we “understand” the metals to be
bonded together.
Draw this diagram quickly…
Metals are understood to exist
as packed cations, surrounded
by loose valence electrons.
These valence electrons can
move quickly (near the speed
of light) if they have to.
The positives balance the
negatives since they are all
atoms. Protons = electrons.
Imagine smashing the metal with a hammer to make the metal exhibit its
malleable nature. The cations will be crushed closer together, and would repel,
but the loose valence electrons flow to offset this excess positive charge.
Same when you squish it into a wire.
Imagine a flow of electrons (electricity) in from the left side. As electrons flow into
the metal, there are too many negative electrons for the cations, so the excess
electrons flow out the other side (the flow of electrons is electricity!).
The cations are awash in a sea of loose valence electrons.
Hand in bonding home work #1 now.
All old work is due asap!
Check your grades.
Read the Diary!