Articles — explaining the periodic table
Why mercury is liquid, why gold is yellow, why fluorine is the most reactive of all elements. Long-form essays that take you behind the obvious.
- Phenomenon6 min read
Why is mercury liquid at room temperature?
Mercury is the only metal liquid at 25 °C. The answer comes down to two words: relativistic effects. A dive into unexpected physics.
- Concept5 min read
How to read (and write) an electron configuration
1s² 2s² 2p⁶… A complete walk-through of the notation, Klechkowski's rule, notorious exceptions, and how to use it to predict an element's chemistry.
- Comparison6 min read
Lanthanides vs actinides: three essential differences
The two 14-element series of the f-block look similar on the surface but diverge profoundly: radioactivity, oxidation states, contraction. A clear side-by-side.
- Phenomenon5 min read
Why is gold yellow (and silver grey)?
Gold and silver are in the same group, with the same valence configuration. Yet one is yellow and the other grey. Another relativistic-effect story.
- Concept7 min read
Rare earths: neither earths nor rare
Cerium is more abundant than copper. Neodymium is more abundant than lead. Why call them 'rare earths' then, and why have they become strategic?
- Concept5 min read
Why does the periodic table have 18 columns and 7 rows?
The table's structure isn't an aesthetic choice. Each dimension directly reflects the quantum numbers of quantum mechanics. Here's the proof.
- Phenomenon6 min read
Why do alkali metals explode in water?
Sodium that ignites, potassium that detonates, cesium that shatters glass. The exact mechanism was clarified in 2015 — and it's not the one taught in class.
- History7 min read
Did Mendeleev really predict elements?
In 1869, Mendeleev left three empty cells in his table and listed precise properties for the elements yet to be discovered. Fifteen years later, he was right — number by number.
- Phenomenon6 min read
Why is fluorine the most reactive of all elements?
Fluorine attacks glass, burns water, oxidizes noble gases. Its off-the-charts reactivity comes from a rare cocktail: high electronegativity AND surprisingly weak F-F bond.
- Phenomenon7 min read
Noble gases: why are they inert (and sometimes not)?
For 70 years it was believed noble gases formed no compounds. Then in 1962 Neil Bartlett accidentally made XePtF₆ — and noble-gas chemistry was born.
- Concept7 min read
Ionization energy: what the first step reveals
Pulling off an atom's first electron costs an energy that reveals its structure. Reading the graph and explaining the anomalies (Be→B, N→O, noble gases).
- Concept7 min read
Electronegativity: three scales, one concept
Pauling, Mulliken, Allred-Rochow: three ways of quantifying the same idea. Why all three exist, which one to use when.