627 articles
All articles — Page 8
Every article in the chemistry library, newest first.
Inside the Atomic Nucleus: Size, Density and the Strong Force
An intermediate guide to the atomic nucleus: Rutherford's discovery, how big nuclei are and how radius scales with mass number, their astonishing density, the strong nuclear force, binding energy and mass defect, the binding energy per nucleon curve, magic numbers, and why some nuclei are radioactive.
Atomic Number: Why the Proton Count Defines an Element
What atomic number is, why the number of protons (and not electrons or neutrons) defines an element, how Henry Moseley discovered it with X-rays, how it orders the periodic table, what changes it in nuclear reactions, and worked examples of using it.
The Shapes of s, p, d and f Orbitals Explained
What atomic orbitals look like and why: spherical s orbitals, dumbbell p orbitals along x, y and z, the five d orbitals including the dz² ring shape, the complex f orbitals, nodes and phases, how orbital size grows with shell number, and why shapes matter for bonding and molecular geometry.
How Is Atomic Radius Measured? Covalent, Metallic and van der Waals Radii
An atom has no hard edge, so how do chemists give it a radius? A clear guide to covalent, metallic, van der Waals and ionic radii, how each is measured, and why the numbers differ.
How Atomic Spectra Tell Us What Stars Are Made Of
How astronomers use atomic spectra to study the universe: Fraunhofer lines, the discovery of helium in the Sun, Cecilia Payne-Gaposchkin's discovery that stars are mostly hydrogen, spectral classes and temperature, redshift and the expanding universe, exoplanet atmospheres and the chemistry of interstellar space.
Atomic Spectra and Photon Energy Practice Problems
Thirteen atomic spectra problems with full worked solutions: photon energy, frequency and wavelength, the Rydberg equation, hydrogen energy levels, ionization energy, series limits, He⁺ and photon counting.
From Atomic Structure to Bonding: Connecting the Ideas
How electron configurations, valence electrons, electronegativity and atomic size explain why atoms form ionic, covalent or metallic bonds, and how those bonds decide the properties of substances.
Atomic Structure Glossary: 60 Key Terms Defined
Sixty essential atomic-structure terms, from alpha particle to Zeeman effect, each defined in plain English with an example and a link to a full explanation. A handy revision reference for students.
10 Misconceptions About Atoms (and What's Actually True)
Ten common misconceptions about atoms corrected clearly: that atoms are solid balls, that electrons orbit like planets, that atoms of a substance share its properties, that atoms are alive, that isotopes are radioactive, that bigger atoms have more electron shells in every case, and more, with the evidence behind each correction.
Atomic Structure Practice Questions: Protons, Neutrons and Electrons
Twenty-five beginner-friendly atomic structure practice questions with full answers: counting protons, neutrons and electrons in atoms, isotopes and ions, completing tables, identifying elements, relative atomic mass, electron shell arrangements and short-answer questions on atomic models.
Atomic Structure Study Guide: Everything for Your Exam
A complete revision guide to atomic structure: subatomic particles, atomic and mass numbers, isotopes and relative atomic mass, the history of atomic models, electron shells and configurations, ions, spectra and ionisation energy, with checkpoint questions, answers and a one-week revision plan linking to every topic.
Atoms vs Molecules vs Compounds vs Elements
Clear definitions and a side-by-side comparison of atoms, elements, molecules, compounds and mixtures, with examples, a decision flowchart, tricky cases like O₂ and NaCl, and quick practice questions.
ATP: The Cell's Energy Currency
What ATP is and why its hydrolysis releases energy: structure, 'high-energy' phosphate bonds explained properly, the ΔG of ATP hydrolysis, energy coupling, how ATP is regenerated, phosphocreatine, and how much ATP your body recycles each day.
The Aufbau Principle: Filling Orbitals from the Bottom Up
What the Aufbau principle says, the order in which subshells fill (1s 2s 2p 3s 3p 4s 3d…), the diagonal rule and the n + l rule for remembering it, why 4s fills before 3d, worked electron configurations, the famous exceptions, and why 4s electrons are lost first when ions form.
Back Titration Calculations Explained
What a back titration is, when to use one, and a step-by-step method for the calculations, with five worked examples: limestone, antacids, ammonia from ammonium salts, aspirin and chloride by Volhard's method.
Base Pairing: A–T and G–C
Why adenine pairs with thymine and guanine with cytosine: hydrogen-bond donors and acceptors, purine–pyrimidine geometry, Chargaff's rules, GC content and melting temperature, base stacking, wobble pairs and why pairing errors cause mutations.
Industrial Bases: Sodium Hydroxide, Lime and Ammonia
The bases that keep industry running: sodium hydroxide, lime, ammonia, sodium carbonate and potassium hydroxide, with how each is made, the scale of production and their key uses from soap to steel.
Bases vs Alkalis: Are They the Same?
Every alkali is a base, but not every base is an alkali. Learn the exact difference, which metal hydroxides dissolve, how to test for each, and the exam answers that earn marks.
The Beer–Lambert Law with Worked Examples
How absorbance depends on concentration, path length and molar absorptivity: A = εcl explained, absorbance vs transmittance, six worked examples, why the law fails at high concentration, and how it's used.
Beer–Lambert Law Practice Problems
Seventeen worked Beer–Lambert practice problems: absorbance and transmittance conversions, finding concentration, molar absorptivity and path length, calibration graphs, dilution factors, mixtures, choosing a wavelength and spotting when the law breaks down.
The Four Major Biomolecules
Carbohydrates, lipids, proteins and nucleic acids compared: their elements, building blocks, bonds, structures, functions and food sources, with a summary table and the condensation–hydrolysis idea that links them.
The Biuret Test for Proteins
A school-lab guide to the biuret test: how copper(II) ions form a purple complex with peptide bonds, a safe method for foods, using a colorimeter to estimate protein concentration, results, limitations and sources of error.
The Blood Buffer: How Your Body Holds pH at 7.4
How the carbonic acid–hydrogencarbonate buffer, proteins and phosphate keep blood between pH 7.35 and 7.45, how lungs and kidneys help, and what goes wrong in acidosis and alkalosis.
Luminol: How Crime Scene Investigators Find Blood
How luminol makes invisible traces of blood glow blue: the chemistry of chemiluminescence, why iron in haemoglobin acts as a catalyst, false positives from bleach and metals, other presumptive blood tests, and what happens after the glow.
Bohr Model Calculations: Energy Levels, Radii and Transitions
Worked Bohr model calculations for hydrogen and one-electron ions: energy of each level, energy of transitions, wavelength and frequency of emitted photons, ionisation energy in J, eV and kJ/mol, orbit radii, scaling with Z² for He⁺ and Li²⁺, and common mistakes.
The Bohr Model: What It Got Right and Where It Fails
Niels Bohr's 1913 model of the atom explained: the problem with Rutherford's atom, Bohr's three postulates, fixed energy levels, how it explained hydrogen's line spectrum, what it got right, why it fails for other atoms and chemical bonding, and why it's still taught today.
Boiling Point Determination
How to measure the boiling point of a liquid in the lab: the distillation method, the Siwoloboff micro method with an inverted capillary, what boiling actually is, correcting for atmospheric pressure, what boiling points say about purity, and common mistakes.
Brønsted–Lowry Acids and Bases
Acids donate protons, bases accept them. A complete guide to the Brønsted–Lowry theory with conjugate pairs, amphoteric water, worked examples and practice questions.
Buffer Calculations: pH After Adding Acid or Base
Step-by-step method for calculating buffer pH before and after adding strong acid or strong base, with worked examples showing how little the pH changes, and what happens when a buffer is overwhelmed.
Buffer Capacity and Buffer Range
How much acid or base a buffer can absorb, why capacity depends on concentration and ratio, the pKa ± 1 buffer range, how to compare buffers numerically, and how to design one for a job.