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Lewis Dot Structures. Gilbert Lewis One of Americas most influential Chemist . Lewis Dot Structures. Gilbert Lewis One of Americas most influential Chemist .

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slide1

Lewis Dot Structures

Gilbert Lewis

One of Americas most influential Chemist.

slide2

Lewis Dot Structures

Gilbert Lewis

One of Americas most influential Chemist.

slide3

He was the first person to speak of electrons being shared rather then transferred. His was the first description of covalent bonding.

slide4

Lewis dot structures help us to understand the shape and structure of atoms. Bonds represent a pair of shared electrons while excess electrons are show in lone pairs

slide5

Step 1

Identify what element are in the formula and how many valence electrons each one contributes to bonding.

slide6

Step 1

Identify what element are in the formula and how many valence electrons each one contributes to bonding.

H2O

slide7

Step 1

Identify what element are in the formula and how many valence electrons each one contributes to bonding.

H2O

H = 1v.e. x 2 = 2

O = 6v.e. x 1 = + 6

Total v.e. available 8

slide8

Step 2

Identify the central atom. Most formulas are written with the central atom first.

The lowest electronegative atom tends to be the central atom.

H is never the central atom.

slide9

Step 2

Identify the central atom. Most formulas are written with the central atom first. The lowest electronegative atom tends to be the central atom. H is not ever the central atom.

H2O

slide10

Step 2

Identify the central atom. Most formulas are written with the central atom first. The lowest electronegative atom tends to be the central atom. H is not ever the central atom.

H2O

O

H

H

Central atom

slide11

Step 3

Draw a single line between the atoms which signify two shared electrons. Each bond removes two v.e. from the amount you started with.

slide12

Step 3

Draw a single line between the atoms which signify two shared electrons. Each bond removes two v.e. from the amount you started with.

Total v.e.

8

H

O

H

slide13

Step 3

Draw a single line between the atoms which signify two shared electrons. Each bond removes two v.e. from the amount you started with.

Total v.e.

8

-4

4

remain

H

O

H

or

..

..

H

O

H

slide14

Step 4

Count and see how many electrons you still need to fulfill the octet rule for each element. Compare this number to how many electrons you have available.

slide15

Step 4

Count and see how many electrons you still need to fulfill the octet rule. Compare this number to how many electrons you have available.

Total v.e.

8

4

remain

H

O

H

H has 2 and only needs 2

It’s good!

slide16

Step 4

Count and see how many electrons you still need to fulfill the octet rule for each element. Compare this number to how many electrons you have available.

Total v.e.

8

4

remain

H

O

H

2

H has 2 and only needs 2

It’s good!

slide17

Step 4

Count and see how many electrons you still need to fulfill the octet rule for each element. Compare this number to how many electrons you have available.

Total v.e.

8

4

remain

H

O

H

2

2

O has 4 and needs 8 so it needs 4 more

slide18

Step 5

*If you have enough electrons left just add them to each element in electron lone pairs.

*If you don’t have enough electrons you must share more electrons by forming additional bonds.

*If you have too many electrons place them on the central atom.

slide19

Step 5

*If you have enough electrons left just add them to each element in electron lone pairs.

..

Total v.e.

4

-4

0

remain

H

O

H

..

Both H’s have 2 and O has 8 they all have full octets with no left over electrons.

slide20

Step 1

Identify what element are in the formula and how many valence electrons each one contributes to bonding.

CO2

slide21

Step 1

Identify what element are in the formula and how many valence electrons each one contributes to bonding.

CO2

C = 4v.e. x 1 = 4

O = 6v.e. x 2 = + 12

Total v.e. available 16

slide22

Step 2

Identify the central atom. Most formulas are written with the central atom first. The lowest electronegative atom tends to be the central atom. H is not ever the central atom.

CO2

slide23

Step 2

Identify the central atom. Most formulas are written with the central atom first. The lowest electronegative atom tends to be the central atom. H is not ever the central atom.

CO2

C

O

O

Central atom

slide24

Step 3

Draw a single line between the atoms which signify two shared electrons. Each bond removes two v.e. from the amount you started with.

Total v.e.

16

O

C

O

slide25

Step 3

Draw a single line between the atoms which signify two shared electrons. Each bond removes two v.e. from the amount you started with.

Total v.e.

16

-4

12

remain

O

C

O

or

..

..

O

C

O

slide26

Step 4

Count and see how many electrons you still need to fulfill the octet rule. Compare this number to how many electrons you have available.

Total v.e.

16

12

remain

O

C

O

O has 2 and needs 6 more

slide27

Step 4

Count and see how many electrons you still need to fulfill the octet rule. Compare this number to how many electrons you have available.

Total v.e.

16

12

remain

O

C

O

2

O has 2 and needs 6 more

slide28

Step 4

Count and see how many electrons you still need to fulfill the octet rule. Compare this number to how many electrons you have available.

Total v.e.

16

12

remain

O

C

O

2

2

C has 4 and needs 4 more

slide29

Step 5

*If you have enough electrons left just add them to each element in electron lone pairs.

*If you don’t have enough electrons you must share more electrons by forming additional bonds.

*If you have too many electrons place them on the central atom.

slide30

Step 5

Count and see how many electrons you still need to fulfill the octet rule. Compare this number to how many electrons you have available.

Total v.e.

16

12

remain

O

C

O

2

2

4

Needs 6

Needs 4

Needs 6

You have 12 electrons left but you still need 16. You don’t have enough and must add more bonds.

slide31

Step 5

Count and see how many electrons you still need to fulfill the octet rule. Compare this number to how many electrons you have available.

Total v.e.

16, 12

10

remain

O

C

O

4

2

6

Needs 4

Needs 2

Needs 6

You have 10 electrons left but you still need 12. You don’t have enough and must add more bonds.

slide32

Step 5

Count and see how many electrons you still need to fulfill the octet rule. Compare this number to how many electrons you have available.

Total v.e.

16, 12, 10

8

remain

O

C

O

4

4

8

Needs 4

Needs 0

Needs 4

You have 8 electrons left and you need 8. You have enough and do not need to add more bonds.

slide33

Step 5

*If you have enough electrons left just add them to each element in electron lone pairs.

*If you don’t have enough electrons you must share more electrons by forming additional bonds.

*If you have too many electrons place them on the central atom.

slide34

Step 5

*If you have enough electrons left just add them to each element in electron lone pairs.

..

..

Total v.e.

8

-8

0

remain

O

C

..

O

..

All three atoms have 8 electrons and have full octets with no left over electrons.

slide35

Hints

*Always make sure the outside atoms have full octets. Place any odd electrons situations on the central atom.

*If you have a polyatomic cation subtract the positive charge from the starting # of valence electrons.

*If you have a polyatomic anion add the negative charge to the starting # of valence electrons

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