A grid of 118 squares, a handful of bonds, and the chemistry that builds rocks, refines copper, prints proteins, and powers everything from your batteries to your breathing.
Mendeleev published it in 1869 with gaps for elements yet to be found. The modern table is organized by atomic number Z and electron configuration: rows are periods (n), columns are groups (similar valence).
Z protons in a tiny nucleus (~10⁻¹⁵ m), N neutrons alongside, Z electrons in shells around (~10⁻¹⁰ m). Mass is overwhelmingly nuclear; chemistry is overwhelmingly electronic.
Schrödinger's equation gives orbitals: 1s, 2s, 2p, 3s, 3p, 3d, ... Aufbau, Pauli, Hund. The shape of the periodic table follows directly from filling these.
s · p · d · f orbitals — sketches of |ψ|² boundary surfaces
Electrons transfer. ΔEN > ~1.7. Lattice energy holds them in a crystal. Brittle, high-melting, conductive when molten or dissolved.
Electrons shared. ΔEN < ~1.7. Discrete molecules. Polarity depends on ΔEN and geometry. Drives organic chemistry.
Cation lattice in a sea of delocalized electrons. Ductile, conductive, lustrous. Drude/free-electron then band theory.
Plus: hydrogen bonds (water, DNA), van der Waals (gecko feet, gas phase), π-stacking (graphite).
R = 8.314 J·mol⁻¹·K⁻¹. Boyle, Charles, Avogadro combined. Holds when intermolecular forces are negligible.
ΔG < 0 → spontaneous at constant T, P. Couples enthalpy (heat) to entropy (disorder).
Cell potential vs. concentrations. F = 96,485 C/mol. The basis of every battery, every neuron's resting potential.
Rate constants rise exponentially with T. Catalysts work by lowering Eₐ.
2 H2 + O2 → 2 H2O
Two or more reactants combine.
2 H2O2 → 2 H2O + O2
One compound splits.
Zn + 2 HCl → ZnCl2 + H2
More-active element displaces another.
AgNO3 + NaCl → AgCl ↓ + NaNO3
Ions swap partners; often a precipitate.
CH4 + 2 O2 → CO2 + 2 H2O
Hydrocarbon meets oxygen, releases heat.
Cu + 2 AgNO3 → Cu(NO3)2 + 2 Ag
Electrons transfer; OIL RIG.
Carbon's four valence bonds, of comparable energy in σ and π configurations, allow chains, rings, branches, and double/triple bonds — yielding the ~10⁸ catalogued organic compounds.
Friedrich Wöhler's 1828 synthesis of urea from ammonium cyanate ended the wall between "organic" and "inorganic."
C6H6 — Kekulé's resonance ring (1865)
1743–94
Conservation of mass; named oxygen, hydrogen.
1834–1907
Periodic Table; predicted Ga, Sc, Ge.
1867–1934
Radioactivity; isolated Po, Ra. 2 Nobels.
1901–94
Nature of the chemical bond; electronegativity.
1910–94
X-ray crystallography of penicillin, B12, insulin.
1920–58
DNA Photo 51, virus structures.
b. 1937
Woodward–Hoffmann rules; orbital symmetry.
b. 1956
Directed evolution of enzymes. Nobel 2018.
Bronze metallurgy in Mesopotamia.
Robert Boyle, The Sceptical Chymist: chemical elements as primary substances.
Lavoisier publishes the Traité élémentaire; oxygen theory of combustion replaces phlogiston.
John Dalton's atomic theory: integer mass ratios.
Mendeleev's periodic table.
Haber–Bosch ammonia synthesis — feeds half the world today.
Niels Bohr's atom; Moseley's atomic numbers.
Watson, Crick, Franklin, Wilkins: DNA double helix.
Buckminsterfullerene C60 — Curl, Kroto, Smalley.
Graphene — Geim, Novoselov; one-atom-thick carbon sheet.
AlphaFold cracks protein folding; CRISPR Nobel; mRNA vaccines roll out.
Rate laws describe how reaction speed depends on concentration: rate = k[A]m[B]n. Order m+n found by experiment.
Equilibrium is the dynamic state where forward and reverse rates equal:
Le Chatelier: stress the system, it shifts to relieve the stress. Cool an exothermic reaction → more product.
Single sheet of sp² carbon; 200,000 cm²/V·s electron mobility; ultimate tensile 130 GPa.
C60 truncated icosahedron — cages, drug delivery, photovoltaics.
Rolled graphene; SWCNT and MWCNT; semiconducting or metallic by chirality.
Metal–organic frameworks. Highest known surface areas (> 7,000 m²/g). Gas storage, catalysis.
Bednorz–Müller cuprates; YBa2Cu3O7 Tc = 92 K. Mechanism unsettled.
Hybrid organic–inorganic ABX3; lab efficiencies past 26 % in 15 years.
Four classes of biomacromolecule: proteins, nucleic acids, carbohydrates, lipids. All built largely from C, H, N, O, P, S — plus a smattering of metals.
Proteins fold from 20 amino acids into ~50,000 distinct shapes in a human cell. Each shape, an enzyme or a structure or a signal.
ATP — adenosine triphosphate — is the universal energy currency: hydrolysis of one phosphoanhydride bond releases ~30.5 kJ/mol.
"Nothing in life is to be feared, it is only to be understood. Now is the time to understand more, so that we may fear less."
ML-designed enzymes (David Baker's lab, RFdiffusion). Synthesis routes proposed by transformer models.
Sulfide and oxide electrolytes replace flammable liquid; Li-anode capacity, fast charge.
KOH cycles, MOFs, electroswing. ~$300/tCO₂ today; targets < $100.
Electrocatalytic N2 reduction at ambient T,P — would replace Haber–Bosch's 1 % of world energy use.
Sharpless/Bertozzi 2022 Nobel. CuAAC, SPAAC. Conjugates drugs to antibodies in vivo.
Isolated metal atoms on supports — maximum atom efficiency, novel selectivity.
Vol. III · 03 · Chemistry — Periodic Grid Edition · 2026.05