LEWIS DOT DIAGRAMS Drawing Covalent Compounds

Drawing Dot Diagrams A dot diagram shows the valence electrons for an atom First, write the symbol for the element.

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

The first two spots for electrons represent the s sublevel the last three sides represent the three orbitals of the p sublevel. Drawing 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

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

Nitrogen

sulfur

silicon

chlorine

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

Single Covalent Bond Single 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 Pair lone 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

H2OH2O

CCl 4

CO 2

HCN

PCl 3

CSF 2

Some molecules have multiple center atoms or none Draw the electron dot structure to figure out how they will bond

C2H4C2H4

H2O2H2O2

O2O2

H2H2