627 articles
All articles — Page 20
Every article in the chemistry library, newest first.
Hydrogen Bonding Explained: Why Water Is So Strange
What a hydrogen bond is, why it only forms with nitrogen, oxygen and fluorine, and how it explains water's high boiling point, floating ice, DNA's double helix and protein shapes.
The Electronegativity Trend: How to Predict Bond Polarity
What electronegativity is, the Pauling scale, why it increases across a period and decreases down a group, and how electronegativity differences tell you whether a bond is nonpolar, polar or ionic.
Significant Figures in Chemistry: Rules and Examples
How to count significant figures, the rules for adding, multiplying and logarithms, when exact numbers don't count, and why sig figs matter in real measurements.
The Alkaline Earth Metals: Group 2 Properties and Uses
Beryllium, magnesium, calcium, strontium, barium and radium: their two outer electrons, trends down group 2, reactions with water, flame colours, and why calcium and magnesium matter so much.
The Most Abundant Elements in Earth's Crust
Oxygen and silicon make up nearly three-quarters of the Earth's crust. Here are the eight elements that make up over 98% of it, why the crust differs from the whole Earth, and what the numbers mean.
Avogadro's Number: What It Is and Why It's 6.022 × 10²³
What Avogadro's number means, where the value 6.022 × 10²³ comes from, how it was measured, why it became exact in 2019, and how big it really is.
Elements Named After Scientists: The People on the Periodic Table
The elements named after real people — from curium and einsteinium to seaborgium and oganesson — who they honour, what each scientist did, and the rules for naming an element after someone.
How Are New Elements Made? Inside the Hunt for Superheavy Atoms
How scientists create new elements by fusing nuclei in particle accelerators, why each new element gets harder to make, how single atoms are detected, and how a discovery is confirmed.
Le Chatelier's Principle: How Equilibrium Responds to Change
What chemical equilibrium is, how Le Chatelier's principle predicts the effect of concentration, pressure and temperature changes, and how the Haber process uses it.
VSEPR Theory: How to Predict Molecular Shapes
How VSEPR theory predicts the 3D shape of molecules from electron pairs, the key shapes and bond angles, why lone pairs squeeze bonds, and worked examples from methane to water.
Ionization Energy: Definition, Trend and the Exceptions Explained
What first ionization energy measures, why it increases across a period and decreases down a group, why boron and oxygen break the pattern, and what successive ionization energies reveal.
The Ideal Gas Law (PV = nRT) Explained With Examples
What each term in PV = nRT means, which value of R to use, worked examples for every variable, and when real gases stop behaving ideally.
Post-Transition Metals: Aluminium, Gallium, Indium, Tin, Thallium, Lead and Bismuth
The 'poor metals' between the transition metals and the metalloids: what they have in common, why they're softer and lower-melting than transition metals, and their uses from cans to touchscreens.
What Is the Rarest Element on Earth?
Astatine is the rarest naturally occurring element in Earth's crust — possibly under a gram at any moment. Here's why, plus the rarest stable elements and why 'rare earths' aren't actually rare.
Strong vs. Weak Acids: What's the Difference?
Why 'strong' and 'concentrated' mean different things, the seven common strong acids, how Ka and pKa measure acid strength, and how to calculate the pH of a weak acid.
How to Find the Number of Protons, Neutrons and Electrons
A simple method for finding protons, neutrons and electrons in any atom, isotope or ion using atomic number, mass number and charge — with worked examples and common mistakes.
How Elements Get Their Names: Gods, Places, Scientists and Colours
Where element names come from — mythology, places, scientists, properties, colours and minerals — with examples for each, plus the IUPAC rules for naming new elements today.
Half-Life Explained: How Radioactive Decay Works
What half-life means, why radioactive decay is predictable in bulk but random for a single atom, how to calculate remaining amounts and elapsed time, and real half-lives from seconds to billions of years.
Reaction Rates and Catalysts: What Makes Reactions Faster?
Collision theory, the five factors that change reaction rate — temperature, concentration, surface area, pressure and catalysts — activation energy, and how enzymes and catalytic converters work.
Metallic Bonding: The Sea of Electrons Explained
How metallic bonding works, the electron-sea model, and how it explains why metals conduct electricity and heat, are shiny, malleable and ductile — plus why alloys are harder.
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.
Empirical vs. Molecular Formula: What's the Difference and How to Find Each
What empirical and molecular formulas are, a step-by-step method for finding both from lab data, and how to handle ratios like 1.5 and 1.33 correctly.
The Platinum Group Metals: Platinum, Palladium, Rhodium, Ruthenium, Osmium and Iridium
Six rare, dense, corrosion-resistant metals that occur together: what makes the platinum group special, how they were discovered, and why catalytic converters, electronics and medicine depend on them.
What Is the Hardest Element? Carbon (as Diamond) and the Hardest Metals
Carbon in the form of diamond is the hardest element. Here's how hardness is measured, why diamond is so hard, why graphite is soft, and which metals are hardest.
Buffers Explained: How Solutions Resist pH Change
What a buffer is, how it neutralizes added acid and base, the Henderson-Hasselbalch equation with worked examples, buffer capacity, and the buffer that keeps your blood at pH 7.4.
Chemical vs. Physical Changes: How to Tell Them Apart
The difference between chemical and physical changes, the five signs of a chemical reaction, tricky examples like dissolving and rusting, and chemical vs. physical properties.
Marie Curie and the Discovery of Polonium and Radium
How Marie and Pierre Curie discovered polonium and radium in 1898 by tracking radioactivity through tonnes of ore, what made the work so remarkable, and the legacy — and dangers — of the elements they found.
Alpha, Beta and Gamma Radiation: What's the Difference?
The three main types of nuclear radiation compared — what each one is, how it changes the nucleus, how far it penetrates, how to write decay equations, and why the danger depends on where the source is.
Exothermic vs. Endothermic Reactions: What's the Difference?
How exothermic and endothermic reactions differ, what enthalpy change (ΔH) means, energy diagrams, why bond breaking absorbs energy, and everyday examples of both.
How to Name Covalent (Molecular) Compounds
The prefix system for naming binary covalent compounds, which element goes first, when to drop 'mono-', common exceptions like water and ammonia, and how to write formulas from names.