Warm Up

• Name the following compound1.Cl02

• Give the following formula2. Disilicon Hexafluoride3. Carbon tetrachloride

Covalent Compounds:Writing Lewis Dot Structures

What are the atoms trying to achieve?

Octet rule = atoms want 8 electrons in their valence shell

Exception #1:Hydrogen and Helium only want 2

Covalent Bonding in H2

Covalent Bonding in H2

HH .. HH..

Two hydrogen atoms, each with 1 electron,Two hydrogen atoms, each with 1 electron,

can share those electrons in a covalent bond.can share those electrons in a covalent bond.

HH :: HH

• Sharing the electron pair gives each hydrogen an electron configuration analogous to helium.

Covalent Bonding in F2

Covalent Bonding in F2

Two fluorine atoms, each with 7 valence electrons,Two fluorine atoms, each with 7 valence electrons,

can share those electrons in a covalent bond.can share those electrons in a covalent bond.

• Sharing the electron pair gives each fluorine an electron configuration analogous to neon.

....

....FF.. FF..:: ::

....

....

FF :: FF:: ::........

....

....

ExampleExampleExampleExample

CC ........

FF::..........

Combine carbon (4 valence electrons) andCombine carbon (4 valence electrons) andfour fluorines (7 valence electrons each)four fluorines (7 valence electrons each)

to write a Lewis structure for CFto write a Lewis structure for CF44..

:: FF::........CC

:: FF::........

:: FF::........:: FF::

....

....

The octet rule is satisfied for carbon and The octet rule is satisfied for carbon and each fluorine.each fluorine.

ExampleExampleExampleExample

It is common practice to represent a covalentIt is common practice to represent a covalentbond by a line. We can rewritebond by a line. We can rewrite

:: FF::........CC

:: FF::........

:: FF::........:: FF::

....

....

....

CCFF

FF

FF

FF

....

............:: ::

:: ::

:: ::

....

asas

So… 2 shared electrons can be rewritten as a single line.The line is called a ‘single bond’.

TRY IT!!1.Draw the lewis dot structure for Phosphorus Triiodide2.Draw it again, this time replacing pairs of shared electrons with a single line.

Phosphorus Triiodide

PI

II

PI

II

.... :

..

::

::: :

:: :

::

::

:: : ::

:

_ __

Double bonds• Some atoms share more than 2 pairs of

electrons between them. • You still replace each pair of shared electrons

with a line but if two lines are present between 2 atoms, it is called a DOUBLE BOND.

CC:: :: ::OO....::OO

....:: ::

Carbon dioxideCarbon dioxide

Try drawing the double bonds for carbon dioxide

CC ::OO....

OO....::

CC:: :: ::OO....::OO

....:: ::

becomes

Triple Bonds

:: :: ::NN::CC::HH ::NNCCHH

Hydrogen cyanideHydrogen cyanide

REMEMBER…

• The atoms want to have 8 valence electrons!• Shared electron pairs can be represented by a

line, which shows that the atoms are bonded.

Let’s

practice!

EthyleneEthylene

AcetyleneAcetylene:: :: ::CC::CC::HH HH

CC:: ::CC....

HH ::::....

HHHHHH

Replace the electron pairs by drawing in the bonds

EthyleneEthylene

AcetyleneAcetylene:: :: ::CC::CC::HH HH CCCCHH HH

CC:: ::CC....

HH :: ::....

HHHHHH

CC CC

HH HH

HHHH