39 articles
The Periodic Table & Elements
Groups, periods, trends and element records — how the table is organised and what it tells you.
The Chalcogens (Group 16): Oxygen, Sulfur, Selenium, Tellurium and Polonium
Group 16 explained: why oxygen is so reactive, sulfur's many forms and uses, selenium's role in the body and electronics, tellurium's rarity, and polonium's radioactive history.
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.
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.
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.
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.
The Atomic Radius Trend: Why Atoms Shrink Across a Period
Why atomic radius decreases across a period and increases down a group, how ionic radii compare, the lanthanide contraction, and how to rank atoms by size in exam questions.
The Actinides: Uranium, Plutonium and the Radioactive f-Block
The 15 actinide elements from actinium to lawrencium: why they're all radioactive, which occur in nature, how the rest were made, and their roles in nuclear power, weapons, medicine and smoke detectors.
Why Is the Periodic Table Shaped Like That?
Why periods have 2, 8, 18 and 32 elements, why there's a gap at the top, why two rows float at the bottom, and the alternative designs — long-form, spiral and 3D — that chemists have proposed.
Rare Earth Elements: What They Are and Why the World Needs Them
The 17 rare earth elements — the lanthanides plus scandium and yttrium — why they aren't really rare, why they're so hard to separate, and their role in magnets, electronics and clean energy.