LEWIS DOT DIAGRAMS

Drawing Covalent Compounds

Drawing Dot DiagramsA dot diagram shows the valence electrons for an atom

First, write the symbol for the element.

Drawing Dot DiagramsThen, put a dot to show each electron in the outer shell, in the following order:

X 36

4758

1 2

• The first two spots for electrons represent the s sublevel

• the last three sides represent the three orbitals of the p sublevel.

Drawing Dot DiagramsDrawing Dot Diagrams

Two Exceptions

Carbon and silicon are exceptions to the pattern

Two exceptions:Carbon and silicon have hybrid orbitals, so their dot diagrams will look like this: C

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An Addendum to Lewis StructuresHybrid orbitals: the s and p sublevels blend together and have four equal energy

Nitrogen

sulfur

silicon

chlorine

Covalent BondingA covalent bond occurs when two nonmetals share electrons.

Covalent Bonding (Review)◦Octet Rule◦ In forming covalent bonds, electron sharing usually occurs

so that atoms can have 8 electrons◦H, Li, Be, and B are exceptions to this…they only want two

Lewis Dot StructuresOR Covalent Bonding Diagram◦Lewis Dot Structure : The structures of molecular compounds can ◦Covalent bonds are shown using dashes◦Dashes represent TWO electrons

Single Covalent BondSingle bond: Sharing a single pair (two) of electrons

Single covalent bond

Multiple Bonds◦Double bond : sharing two pairs (four) of electrons◦Triple bond : sharing three pairs (6) of electrons

◦Multiple covalent bonds usually occur in atoms that conatin carbon, nitrogen, and oxygen

Unshared Pairlone pair A pair of valence electrons THAT DOES NOT BOND

Lone pair

Each fluorine atom has 3 lone pairs

Drawing Lewis Structures◦I am going to go through the steps of drawing lewis structures, the steps are also written on the board. ◦There are 6 steps

Drawing Lewis Structures for Covalent Compounds

1. Determine the total # of valence electrons for all atoms

2. Draw the electron dot structures for all the elements

3. Choose the center atom-The least lone pairs- Carbon is always the center-Hydrogen is never the center

4. Place the outside atoms around the center and indicate a shaired pair with a dash

5. All atoms must have 8 electrons around then (except for H)

5. Make sure your covalent bond structure has the same number of electrons as you calculated

H2O

CCl4

CO2

HCN

PCl3

CSF2

Some molecules have multiple center atoms or none

Draw the electron dot structure to figure out how they will bond

C2H4

H2O2

O2

H2