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# Lewis Dot Structure - PowerPoint PPT Presentation

How to create a…. Lewis Dot Structure. …for CH 4. #1 Count the total number of valence electrons in the molecule C: 4 electrons x 1 atom = 4 valence electrons H: 1 electron x 4 atoms = 4 valence electrons Total = 8 valence electrons. How to create a…. Lewis Dot Structure. …for CH 4.

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## PowerPoint Slideshow about ' Lewis Dot Structure' - thao

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Lewis Dot Structure

…for CH4

• #1 Count the total number of valence electrons in the molecule

• C: 4 electrons x 1 atom = 4 valence electrons

• H: 1 electron x 4 atoms = 4 valence electrons

• Total = 8 valence electrons

Lewis Dot Structure

…for CH4

• #2 Find the number of “octet” electrons for the molecule.

• C: 8 octet electrons x 1 atom = 8 octet electrons

• H: 2 octet electrons x 4 atoms = 8 octet electrons

• Total = 16 octet electrons

• Rules: Hydrogen always has 2 octet electrons

• Beryllium always has 4 octet electrons

• Boron wants 6 for neutral molecules (8 if it’s an anion)

Lewis Dot Structure

…for CH4

#3 Subtract the number of valence electrons from the number of octet electrons to find the number of bonding electrons.

16 – 8 = 8 bonding electrons

Lewis Dot Structure

…for CH4

• #4 Divide the number of bonding electrons by 2 to find the number of bonds in the molecule.

• 8 / 2 = 4 bonds in CH4

• Why 2?

• Because there are two electrons in every covalent bond!

Lewis Dot Structure

…for CH4

#5 Draw an arrangement of atoms that has the number of bonds you found in step 4. Of course, there are more rules…

Hydrogen and Halogens = bond once!

Oxygen’s family and Beryllium bond twice in neutral molecules

Nitrogen’s family and Boron bond 3 times in neutral molecules

Carbon’s family = bonds 4 times!

Lewis Dot Structure

…for CH4

More hints…

If you bond everything together and you have bonds left over, look for double/triple bonds.

The atom nearest to the left side of the periodic table is probably in the middle of the molecule.

H2O

CCl4

NH3

CO2

PCL3

N2

CH4

C2H6

CH3OH

BH3

PBr3

N2H2

C2H2

SiH4

C2H4

HF

HCl

CCl2F2