105 articles
Atomic Structure
Protons, neutrons, electrons, orbitals and electron configurations — what atoms are made of and how their electrons are arranged.
Mass Defect and Nuclear Binding Energy Calculations
Worked examples calculating mass defect and nuclear binding energy with E = mc²: helium-4, carbon-12, iron-56 and uranium-235, binding energy per nucleon, converting between u, kg, J and MeV, energy released in fusion and fission, and why iron-56 is so stable.
Radial and Angular Nodes in Atomic Orbitals
What nodes in atomic orbitals are, how to count radial and angular nodes with the formulas n − l − 1 and l, worked examples from 1s to 5f, nodal planes and cones, radial probability graphs, why nodes raise orbital energy, phases and why nodes matter for bonding and spectroscopy.
The Band of Stability: Why Some Nuclei Are Stable
Why is carbon-12 stable but carbon-14 radioactive? A guide to the band of stability: neutron-to-proton ratios, magic numbers, even–odd effects, and how a nucleus's position predicts its decay mode.
Photoelectric Effect Calculations: Work Function and Kinetic Energy
Worked examples using Einstein's photoelectric equation hf = φ + KE_max: threshold frequency and wavelength, maximum kinetic energy and speed of photoelectrons, stopping potential, working in joules and electronvolts, reading a KE vs frequency graph to find Planck's constant, and intensity questions.
Quantum Chemistry Misconceptions
Nine persistent myths about quantum mechanics in chemistry, from electrons as tiny planets and spinning balls to 'observation creates reality' and hybrid orbitals as physical objects, each with the correct picture explained.
Relativistic Effects in Chemistry: Why Mercury Is Liquid
How Einstein's relativity changes the chemistry of heavy elements: fast inner electrons, the contraction of s orbitals and expansion of d and f orbitals, why gold is yellow and noble, why mercury is a liquid, the inert pair effect in thallium and lead, relativity in car batteries, and what it means for superheavy elements.
The Rydberg Equation with Worked Examples
How to use the Rydberg equation 1/λ = R(1/n₁² − 1/n₂²) for hydrogen and one-electron ions: the Rydberg constant, calculating wavelengths of Lyman, Balmer and Paschen lines, finding the upper level from a wavelength, series limits, ionisation energies and common mistakes.
The Schrödinger Equation: What Chemists Actually Need to Know
A chemist's guide to the Schrödinger equation without heavy mathematics: what Ĥψ = Eψ means, the Hamiltonian and wavefunction, why solutions give quantised energies, the particle in a box, what the hydrogen atom solutions produce (orbitals and quantum numbers), approximations for many-electron atoms and molecules, and computational chemistry.
Slater's Rules: Calculating Effective Nuclear Charge Step by Step
Worked examples of Slater's rules for estimating shielding and effective nuclear charge: grouping orbitals, shielding contributions for s/p and d/f electrons, calculations for nitrogen, sodium, chlorine, zinc and potassium, using Zeff to explain 4s vs 3d and ionisation trends, and the rules' limitations.
Term Symbols and Spectroscopic Notation for Beginners
What does ³P₀ or ⁵D₄ mean? A step-by-step method for writing the ground-state term symbol of any atom using Hund's rules, with worked examples from carbon to iron and practice questions.
Transition Metal Electron Configurations: 4s, 3d and Ions
Worked configurations for every first-row transition metal from scandium to zinc, with the chromium and copper exceptions explained, how to write their common ions, why 3d and 4s energies cross, how configurations explain variable oxidation states, colour and magnetism, and second- and third-row surprises.
The Zeeman Effect: How Magnetic Fields Split Spectral Lines
Put a glowing gas in a magnetic field and its sharp spectral lines split into several. Learn why the Zeeman effect happens, how big the splitting is, why it revealed electron spin, and how astronomers use it to map sunspots.
Electron Configuration Exceptions: Why Chromium and Copper Break the Rules
Why chromium is [Ar] 4s1 3d5 and copper is [Ar] 4s1 3d10, the stability of half-filled and filled d subshells, the full list of common exceptions, and why the heavier elements have even more.
Quantum Numbers Explained: n, l, mₗ and mₛ
The four quantum numbers that describe every electron in an atom, what each one means, the allowed values, how they connect to shells, subshells and orbitals, and worked examples.
Why Is Gold Yellow? Relativity and the Colour of Metals
Almost every metal is silvery grey, but gold is yellow and copper is reddish. The explanation involves electrons moving at a significant fraction of the speed of light — here's how relativity colours gold.