Electronegativity and Polarity
Rank the following bonds from least polar to most polar:
C–H, C–Cl, H–F
C–H < C–Cl < H–F
Draw the Lewis structure for NO₂⁻.
Predict the geometry of BeCl₂.
Linear, 180°
Determine the hybridization of carbon in CO₂.
sp
Which molecule violates the octet rule?
CO₂, PCl₅, NH₃, CH₄
PCl₅
Using electronegativity values, explain why HF has a larger dipole moment than HCl.
Fluorine is more electronegative than chlorine, producing a larger ΔEN and stronger bond dipole.
Calculate the formal charge on nitrogen in NH₄⁺.
+1
Predict both the electron geometry and molecular geometry of SF₄
Electron geometry:
Trigonal bipyramidal
Molecular geometry:
Seesaw
Determine the hybridization of sulfur in SO₂.
sp2
How many resonance structures exist for NO₃⁻?
3 equivalent resonance structures
A bond has ΔEN = 1.2. What type of bond is it?
Polar Covalent
Which Lewis structure is preferred?
Structure A:
Formal charges = +1, –1
Structure B:
All formal charges = 0
Structure B
Explain why XeF₂ is nonpolar despite containing polar bonds.
Linear geometry allows the two bond dipoles to cancel.
How many σ and π bonds are present in benzene?
12 σ
3 π (delocalized)
Determine all of the following for SO₃:
Lewis structure, Hybridization, Geometry, Bond angles, Polarity
Trigonal planar, 120°, sp², Resonance, Nonpolar
Explain why C–F bonds are polar while CF₄ is a nonpolar molecule.
Each C–F bond is polar because of the large electronegativity difference, but the tetrahedral geometry is perfectly symmetrical, causing the bond dipoles to cancel.
Draw the Lewis structure of SO₄²⁻ including all resonance structures.
Which molecule has the largest bond angle?
NH₃, CH₄, CO₂, H₂O
CO₂ (180°)
According to Valence Bond Theory, why is a σ bond stronger than a π bond?
Head-on overlap produces greater orbital overlap than side-by-side overlap.
Which has the shortest bond?
C–C
C=C
C≡C
C≡C
Using Pauling electronegativities, rank the following bonds in order of increasing polarity:
C-H, C-Cl, C-F, C-Br
C-H< C-Br< C-Cl< C-F
Why is minimizing formal charge more important than simply satisfying octets?
Lower formal charges generally correspond to lower-energy, more stable structures that better represent electron distribution.
Determine: Geometry, Bond angle(s), Polarity for ClF₃.
Electron geometry:
Trigonal bipyramidal
Molecular geometry:
T-shaped
Angles:
~90° and 180°
Polar
Determine the hybridization of every atom in CH₂=CHCN.
CH₂ carbon = sp², CH carbon = sp², Carbon in CN = sp, Nitrogen = sp
For SCN⁻ (thiocyanate ion) determine:
Lewis structures:
⁻S–C≡N
S=C=N⁻
Major contributor:
⁻S–C≡N
Formal charges:
Major structure:
S = –1
C = 0
N = 0
Hybridization:
S = sp²
C = sp
N = sp
Geometry:
Linear
σ bonds = 2
π bonds = 2