Tuesday, 22 March 2016
Aim: To learn to draw a Lewis Structure
Watch the videos
Video: Introduction to Chemical Bonding
Video: Covalent Bonding as taught be a water drop!
Video: Particle Theory of Matter (Song)
Tuesday, 22 March 2016
Aim: To learn to draw a Lewis Structure
Copy the notes below
• Lewis Structures
– Shows the valence electrons in a covalent
molecule (one with shared electrons)
– Electrons are in pairs
• Bonding pairs
• Non-bonding pairs
Tuesday, 22 March 2016
Aim: To learn to draw a Lewis Structure
Copy the notes below
• Steps for drawing a Lewis Structure
– Count up the number of valence electrons
• H has 1, others have their group number – 10
– Draw the atom symbols with the single atom in
the centre
– Put a pair of electrons between each atom
– Put electrons around the out atoms to complete
their outer shells; H needs 2, others need 8.
– Put any extra electrons around the central atom
– Share electrons from outer atoms with central
atom (if required) to make 8.
Tuesday, 22 March 2016
Aim: To learn to draw a Lewis Structure
Watch the demonstration of drawing a Lewis Structure
• Methane (Natural Gas)
• Number of bonding electrons = 4+1+1+1+1 = 8
•
Tuesday, 22 March 2016
Aim: To learn to draw a Lewis Structure
Watch the demonstration of drawing a Lewis Structure
Put a pair of electrons between each H and the
C atom to join them
Tuesday,
March
2016 of:
Draw the22
Lewis
Structure
Make sure each hydrogen has 2 electrons
around it and the carbon atom has 8 electrons
Tuesday, 22 March 2016
Aim: To learn to draw a Lewis Structure
Try to draw the Lewis structures of the molecules below; then
watch the videos to see if you did it right
NH3 and H2CO
Drawing the Lewis Structure of ammonia
Video on H2CO
Tuesday, 22 March 2016
Aim: To learn to draw a Lewis Structure
Watch the demonstration of drawing a Lewis Structure
There are 5+1+1+1 = 8 electrons
When 6 have been used to join atoms put
the other two on the central atom
Tuesday, 22 March 2016
Aim: To learn to draw a Lewis Structure
Watch the demonstration of drawing a Lewis Structure
There are 1+1+4+6 = 12 electrons
When 6 have been used to join atoms put
the other two on the oxygen atom – to give
it 8
Tuesday, 22 March 2016
Aim: To learn to draw a Lewis Structure
Watch the demonstration of drawing a Lewis Structure
The C atom only has 6 electrons around it –
it wants 8; so the oxygen atom shares 2
with the carbon atom. This makes a
“double bond”.
Tuesday, 22 March 2016
Aim: To learn to draw a Lewis Structure
Draw these Lewis Structures test yourself
•
•
•
•
Water H2O
Carbon Dioxide CO2
Ethyne HCCH (has two central atoms)
Carbon Monoxide CO
Tuesday, 22 March 2016
Aim: To learn to draw a Lewis Structure
Check your Lewis Structures
Tuesday, 22 March 2016
Aim: To learn to draw a Lewis Structure
Check your Lewis Structures
Tuesday, 22 March 2016
Aim: To learn to draw a Lewis Structure
Check your Lewis Structures
Tuesday, 22 March 2016
Aim: To learn to draw a Lewis Structure
Check your Lewis Structures
Count up the electrons in outer shells
Put a pair of electrons between each atom
Move the rest to the C atoms (Hs have enough)
Tuesday, 22 March 2016
Ethyne HCCH
Share electrons between C atoms
Tuesday, 22 March 2016
Aim: To learn to draw a Lewis Structure
Check your Lewis Structures
Tuesday, 22 March 2016
Aim: To learn to draw a Lewis Structure
Check your Lewis Structures
Tuesday, 22 March 2016
Aim: To learn to draw a Lewis Structure
Check your Lewis Structures
Tuesday, 22 March 2016
Aim: To learn to draw a Lewis Structure
Check your Lewis Structures