Why does ice float on water?

Due to polar hydrogen bonding, water molecules form a rigid crystalline lattice when freezing. This lattice keeps the molecules farther apart than they are in liquid form, making ice less dense than liquid water.

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Core Study Guide

Molecules & Bonding

How atoms interact to form compounds.

Atoms bond to achieve stable outer electron configurations, usually resembling noble gases (the Octet Rule).

This unit covers ionic bonds (electron transfer), covalent bonds (electron sharing), Lewis structures, and molecular polarity.

Key Takeaways

•Ionic bonds form between metals and non-metals through electrostatic attraction.
•Covalent bonds form between non-metals sharing electron pairs.
•Polar bonds occur when electronegativity differences cause unequal sharing.

Core Concepts & Definitions

1Types of Chemical Bonds

Bonding style is determined by electronegativity differences.

•Ionic: electronegativity difference > 2.0 (complete electron transfer).

•Covalent: electronegativity difference < 1.7 (sharing of electrons).

Quick Revision Notes

•The Octet Rule: atoms tend to gain, lose, or share electrons to have 8 valence electrons.
•Electronegativity is the relative ability of an atom to attract shared electrons in a chemical bond.