Chemistry
Atoms and the periodic table
Atomic structure, nucleus and electrons, periods and groups.
Basics
Atom
An atom has a nucleus of protons and neutrons, surrounded by electrons. The proton count (atomic number Z) defines the element; mass number is protons plus neutrons.
Isotopes
Atoms of the same element (same Z) with different neutron counts. Chemistry is similar; mass and radioactivity can differ.
Periodicity
Left to right: radius usually falls; ionization energy and electronegativity rise. Top to bottom: radius rises; ionization energy falls. Groups share valence electron counts, so similar chemistry.
Electron configuration
Orbitals are s, p, d, f. Aufbau, Pauli exclusion, and Hund’s rule apply. Valence electrons largely set bonding and oxidation numbers.
Formulas
Mass number
Nucleon count = protons + neutrons.
Symbols
-
Amass number -
Zatomic number (protons) -
Nneutron count
Average atomic mass
Weighted mean of isotope masses by abundance.
Symbols
-
fᵢfractional abundance -
mᵢisotope mass
Key table
| Group 1 | Alkali metals — 1 valence electron, highly reactive |
|---|---|
| Group 17 | Halogens — 7 valence electrons, readily form anions |
| Group 18 | Noble gases — closed shells |
| Electronegativity | F > O > N ≈ Cl on the Pauling scale |
In this field
Chemical bonding
Ionic, covalent, and metallic bonds, plus molecular shape.
The mole and stoichiometry
Moles, molar mass, empirical formulas, and yield.
Gases and acids–bases
Ideal gas, pH, and buffers.
Thermo, equilibrium, kinetics
Enthalpy, Gibbs energy, K, and rate laws.
Electrochemistry and organic basics
Oxidation numbers, cells, Nernst, functional groups.
Nuclear chemistry
Radioactivity, half-life, binding energy.
Solutions and kinetics
Concentration, colligative properties, rate laws.
Analytical chemistry
Titration, spectroscopy, and chromatography — measuring what is present and how much.
Polymers and solids
Crystals and glasses, metal–ionic–covalent solids, polymer chains and the glass transition.
Coordination compounds
Ligands, coordination number, crystal field, colour, and an 18-electron sketch.
Electrochemical cells
Galvanic versus electrolytic, Nernst, Faraday, and a corrosion sketch.
Phase equilibria and diagrams
Gibbs phase rule, unary diagrams, eutectics, and the lever rule.