compare electronegativity
🔷AP CHEMISTRY STUDY GUIDE
Unit 2: Compound Structure and Properties
Study ionic solids, covalent bonds, Lewis diagrams, electron delocalization, formal charge, and molecular geometry for AP Chemistry Unit 2.
8 key ideas8 flashcards5 practice questions
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Bonds give vectors. Geometry decides the total.
place bond dipoles in space
add the vectors
Key ideas to know
Start with the relationships between ideas. Then close the notes and explain each one from memory.
- 01
Ionic bonding arises from electrostatic attraction among oppositely charged ions in a lattice.
- 02
Covalent bonding occurs when atoms share electron density.
- 03
Bond order relates to bond length and bond energy.
- 04
Lewis diagrams track valence electrons, bonds, and lone pairs.
- 05
Formal charge helps compare plausible electron arrangements.
- 06
Two or more valid Lewis contributors can represent delocalized electron density.
- 07
VSEPR predicts electron-domain and molecular geometry from repulsions around a central atom.
- 08
Bond polarity and molecular geometry together determine whether a molecule has a net dipole.
PART OF THE AP CHEMISTRY GUIDE
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Open the full AP Chemistry guide →Two ideas worth correcting now
NOT QUITE
→A molecule does not flip between separate Lewis contributors
USE THIS INSTEAD
The diagrams are contributors to one delocalized electron distribution.
NOT QUITE
→A molecule with polar bonds must be polar
USE THIS INSTEAD
Molecular geometry can cause bond dipoles to cancel.
Flashcards
Answer before opening each card. The effort to retrieve is part of the learning.
1What is lattice energy?Show answer ＋
Energy associated with separating one mole of an ionic solid into gaseous ions, or the reverse formation process under the stated convention.
2How does bond order affect bond length?Show answer ＋
Higher bond order usually corresponds to a shorter bond.
3What is formal charge?Show answer ＋
Valence electrons minus nonbonding electrons minus half the bonding electrons.
4What does electron delocalization mean?Show answer ＋
Electron density is spread across several atoms and may require more than one valid Lewis contributor.
5What geometry has four electron domains and no lone pairs?Show answer ＋
Tetrahedral.
6What geometry has three bonds and one lone pair around a central atom with four domains?Show answer ＋
Trigonal pyramidal.
7When is a bond polar?Show answer ＋
When bonded atoms have different electronegativities and share electron density unequally.
8Why can carbon dioxide have polar bonds but no net dipole?Show answer ＋
Its linear bond dipoles have equal magnitude and opposite directions.
Explain it in your own words
Use the answer as a check after you have written or spoken your response.
01Why does magnesium oxide usually have stronger ionic attraction than sodium chloride?
Its ions have greater charge magnitudes, producing stronger electrostatic attraction when distance is comparable.
02How can formal charge help select a Lewis diagram?
Arrangements with smaller formal-charge magnitudes and negative charge on more electronegative atoms are often favored.
03Why can two bonds be equivalent when Lewis contributors show different bond orders?
The actual electron density is delocalized and is represented by all valid Lewis contributors together.
04How do lone pairs affect bond angles?
Lone pairs occupy more space near the central atom and usually compress angles between bonds.
05Why is water polar while carbon dioxide is nonpolar?
Water is bent, so its bond dipoles do not cancel. Carbon dioxide is linear, so they cancel.
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