Foundations

Element mass ratios become atom ratios through molar masses, with uncertainty and sample identity retained.

A Lewis diagram accounts for bonding and nonbonding valence electrons in a specified connectivity.

VSEPR distinguishes the arrangement of electron regions from the positions of atoms.

Polar bonds can cancel in a molecule; molecular geometry matters.

Dissolution disperses specified molecular or ionic species in a solvent.

A saturation limit is an equilibrium property under specified conditions, not a synonym for concentration.

Ordinary filtration separates undissolved particles; dissolved species can remain in the filtrate.

Distillation uses vapor–liquid partitioning and condensation, with a limit at an azeotrope.

Substrate recognition and catalysis depend on a dynamic molecular environment.

Covalent subunit linkage and water-assisted cleavage explain biological polymer structure.

Sugar connectivity distinguishes energy-storage and structural polysaccharides.

Lipids include several architectures rather than one repeating-monomer polymer class.

The peptide backbone and variable side chains are different parts of protein structure.

Bases carry sequence information on a chemically directional sugar–phosphate backbone.