Unit 1: Structure and Bonding
Why molecules take the shape they do: Lewis structures, resonance, hybridization, and the functional groups the rest of the course is built from.
6 topics · 21 questions
Each topic is a path, not a menu: work down it in order and every question builds on the one above. Click any of them to watch the answer draw itself.
Lewis Structures and Formal Charge
- How it worksHow do you count valence electrons to assign a formal charge to each atom in a Lewis structure?
- Worked exampleWalk me through drawing the Lewis structure of the nitrate ion NO3- and assigning every formal charge.
- Common mistakeWhy isn't a big formal charge on an atom the same thing as that atom carrying a full ionic charge?
- Going furtherWhat happens to the formal charges in a structure when a lone pair moves into a π bond instead?
Your turn1 of 2
In a Lewis structure, a particular atom has 6 valence electrons in its neutral, isolated form. In the drawn structure it carries 2 lone pair(s) and participates in 4 total bond(s) to other atoms (count a double bond as 2 and a triple bond as 3). What is that atom's formal charge?Resonance Structures and Delocalization
- How it worksHow do you push electrons with curved arrows to generate one resonance structure from another?
- Common mistakeWhy isn't a molecule actually flipping back and forth between its different resonance structures?
- Common mistakeWhy doesn't moving an atom's position from one drawing to the next count as a resonance structure?
- Going furtherWhat happens to a molecule's stability when it has many resonance structures instead of just one?
Your turn1 of 2
Acetate ion, CH3COO-, is drawn as two resonance structures with the negative charge placed on a different oxygen in each. What is actually true of the real molecule?Hybridization: sp3, sp2, and sp
- How it worksHow do one s orbital and three p orbitals mix together to build four identical sp3 orbitals?
- Worked exampleWalk me through assigning the hybridization of every carbon in propene, CH2 equals CH-CH3.
- Going furtherWhat happens to a carbon's bond angle as its hybridization changes from sp3 to sp2 to sp?
Your turn1 of 2
A carbon's hybrid orbitals are built by mixing one s orbital with 2 p orbital(s), where n = 1 gives sp, n = 2 gives sp2, and n = 3 gives sp3. What percent s-character does each resulting hybrid orbital have?VSEPR and Molecular Geometry
- How it worksHow do lone pairs push bonding pairs around to set a molecule's final geometry?
- Worked exampleFind the electron geometry and the molecular geometry around the nitrogen in ammonia, NH3.
- Common mistakeWhy isn't a lone pair invisible just because it never appears in a molecular geometry's name?
Your turn1 of 2
Ammonia, NH3, has one lone pair and three N-H bonds around its nitrogen. What are its electron geometry and its molecular geometry?Electronegativity and Bond Polarity
- How it worksHow does a difference in electronegativity pull shared electrons closer to one atom in a bond?
- Worked exampleFind which end of the bond carries the partial negative charge in H-Cl using electronegativities 2.1 and 3.0.
- Going furtherWhat happens to a bond's character as the electronegativity gap between its two atoms keeps growing?
- Common mistakeWhy isn't a polar bond automatically the same thing as a polar molecule?
Your turn1 of 2
A bond forms between an atom with electronegativity 3 and an atom with electronegativity 2.52. What is the magnitude of the electronegativity difference across that bond?Functional Groups: The Reactive Parts of a Molecule
- How it worksHow does an electron-rich or electron-poor functional group decide what reaction a molecule undergoes?
- Worked exampleWalk me through identifying every functional group in a molecule that has an ester, a hydroxyl, and a double bond.
- Ties togetherHow does spotting a carbonyl group in a structure predict which later reactions in the course apply to it?
Your turn1 of 2
A molecule contains an ester group, a free hydroxyl group, and an isolated, unactivated carbon-carbon double bond elsewhere in the chain. Which functional group is the strongest electrophile toward an incoming nucleophile?