Lewibs Dot Structure - Chemical Bonding

Introduction

Topic: Lewis Dot Structure for chemical bonding.
Goals: Understanding and drawing structures for ions such as carbonate (CO3 2-) and sulfate (SO4 2-).
Key Learning: Determining single/double bonds, charges, and applying octet rule.

Show only outermost electrons: Represent only the valence electrons in the structure.
Based on Octet Rule: Atoms strive for 8 electrons in valence shell (except hydrogen, which aims for 2).
Covalent and Coordinate Bonds: Sharing electrons to form single, double, triple bonds. Coordinate bond involves lone pair donation.
Valence Shell Logic: Focus on how atoms achieve stable electronic configurations.

Rule for Selecting Central Atom: Central atom is usually the least in number, least electronegative, largest in size, or highest atomic number. Hydrogen and fluorine are never central atoms.
Complete Octet of Corner Atoms: Ensure corner atoms' valence shells are filled first (8 electrons for most atoms, 2 for hydrogen).
Central Atom Electrons: Central atom can have 8 or more electrons; typical valency considerations for central atoms need to be checked (e.g., oxygen max valency is 2).
Charge Distribution: Positive charge generally on central atom; negative charge on corner atoms.

Maximum Covalency: Central atom tries to achieve maximum covalency possible (e.g., nitrogen max. covalency is 4 despite its ability to form 5 bonds theoretically).
Exceptions: Hydrogen and Fluorine can't be central atoms.
Formal Charge Calculation:
- Formula: Formal Charge = Valence Electrons - Lone Pair Electrons - Bond Pair Electrons / 2
- Applied for each individual atom to determine real vs. formal charges.

Carbon Dioxide (CO2): Shows how double bonds work and ensure octets are complete.
Water (H2O): Shows bonding with lone pairs filling oxygen’s remaining valence slots.
Nitrate Ion (NO3-): Resonance and formal charge calculations for more complex ions.
Ammonium Ion (NH4+): Positive charge allocation and bonding pattern determination.
Phosphate Ion (PO4 3-): Includes both resonance consideration and formal charge application.

Sulfur Dioxide (SO2): Central atom (Sulfur) exceeds the octet rule but achieves a stable configuration.
Oxygen molecule (O2): Demonstrates typical double bond formation and lone pair placements.
Hydronium Ion (H3O+): Showcases central oxygen with hydrogen bonded; rationalizes formal charge placement.

Handling Polyatomic Ions: Ensure to add/subtract electrons for given charges before starting structure formation.
Central Atom Flexibility: Central atom might break the octet rule (common in larger central atoms like sulfur or phosphorus).
Common Pitfalls: Performing Resonance Adjustment properly: For ions with resonant structures, make sure to show all valid resonance forms correctly.
Configuration Consistency: Stick to valence and bonding rules consistently to avoid error.

Practice: Draw at least 15 examples repeatedly to gain confidence. Include common ions and various bonding scenarios.
Focus on Octet Rule and Formal Charge: Master these two concepts as they are key in determining correct structures.
Central Atom Strategies: Remember reasons behind selecting central atoms and exceptions.
Formal Charges: Properly calculating and assigning formal charges help indicate the most stable structure conformationally.

By following these strategies and rules, you are well-prepared to tackle any Lewis Dot Structure questions that come your way.