lewis structures
Download
Skip this Video
Download Presentation
Lewis Structures

Loading in 2 Seconds...

play fullscreen
1 / 11

Lewis Structures - PowerPoint PPT Presentation


  • 74 Views
  • Uploaded on

Lewis Structures. 1. Start by determining the formula and the total number of valence electrons. 2. The central atom is the 1 st element in the formula. - It will never be hydrogen. Carbon is always the central atom. 3. Connect the central atom to the outer atoms with a single bond.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' Lewis Structures' - gyula


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
lewis structures
Lewis Structures

1. Start by determining the formula and the total number of valence electrons.

2. The central atom is the 1st element in the formula.

- It will never be hydrogen. Carbon is always the central atom.

3. Connect the central atom to the outer atoms with a single bond.

lewis structures1
Lewis Structures

4. Determine the number of remaining electrons.

  • Number from #1 – (# Bonds x 2)

5. Place the remaining electrons around the outer atoms so each obeys the octet rule.

  • A bond counts as 2 electrons.
lewis structures2
Lewis Structures

6. Any remaining electrons go on the central atom.

7. Check to make sure each atom obeys the octet rule.

- If the central atom does not, take a pair from an outer atom and make a double bond with the central atom.

slide4

- -

-

- -

-

Li

H

He

VSEPR Theory

  • new theory:
  • Valence Shell Electron Pair Repulsion
  • “push” electron pairs as far away from each other as possible
    • electrons repel each other
    • like Thomson model of atom
slide5

look at groups of electrons

    • any collection of valence electrons localized around central atom
    • each electron group repelled by every other e- group
    • can be comprised of
      • unpaired electrons
      • bonding electrons
  • bonding
  • 1 group = single bond
  • 1 group = double bond
  • 1 group = triple bond
  • unpaired
  • 1 group = a single electron
    • e.g. free radical
  • 1 group = 1 lone pair
slide6

VSEPR “rules” for predicting geometry:

    • 1. start with valid Lewis dot structure
      • in case of resonance structures, any valid structure will give same geometry
    • 2. count number of electron groups around central atom
    • 3. determine number of bonding vs. unbonded electron groups
    • 4. describe molecular geometry
      • learn chart
      • see Table 9.2
slide7

180o

2

2

0

linear

CO2

line

120o

3

3

0

trigonal

planar

BF3

triangle

••

120o

trigonal

planar

bent

3

2

1

SO2

boomerang

  • possible geometries:

total #

e- groups

#

bond

#

lone pairs

molecular

geometry

structure

e.g.

slide8

109.5o

CH4

pyramid

4

4

0

tetrahedral

total #

e- groups

#

bond

#

lone pairs

molecular

geometry

structure

e.g.

slide9

total #

e- groups

#

bond

#

lone pairs

molecular

geometry

structure

e.g.

109.5o

CH4

pyramid

4

4

0

tetrahedral

••

<109.5o

4

3

1

tetrahedral

trigonal

pyramidal

NH3

tripod

••

<109.5o

tetrahedral

bent

4

2

2

H2O

“v”

••

trigonal bipyramidal
TrigonalBipyramidal
  • 5 Total electron groups
  • 5 bonding groups
  • 0 lone pairs
octahedral
Octahedral
  • 6 Total electron groups
  • 6 Bonded
  • 0 Lone Pairs
ad