CH28 – More Lewis

Dates

• P4 – Tuesday, October 31st
• P5 – Tuesday, October 31st
• P7 – Wednesday, October 31st

Review Lewis Structures

• H / F bond only once
• C / N / O / F always follow octet
• C never lone pairs
• Metals happy when partners happy

New Idea – Formal Charge

• FC = start – assigned
• assigned = lone electrons + half of bond electrons
• goal – help decide which is better
• example = carbon dioxide

New Idea – Ions

• how do I represent ions?
• example = nitrate ion

New Idea – Resonance

• what to do when two structures equivalent
• example = nitrate ion

New Idea – Exceptions to the Octet

• more than 8 (sulfur hexafluoride)
• less than 8 (aluminum hydride)

Practice, Practice, Practice

For Each Substance (Two substances per side of page)

• total number of valence electrons
• Lewis dot structure
• formal charges (each element)
• central atom lone pairs / bonding pairs
• central atom bonding domains / lone pairs