Chemistry · Periodic Classification Of Properties · NEET
It is a spiral (helix) line drawn on the surface of a cylinder. De Chancourtois wrote the elements along this spiral in order of increasing atomic weight. Because the line wraps around the cylinder, elements come back to the same vertical column after a full turn. Elements sitting on the same vertical line had similar properties. The name 'telluric' comes from tellurium, an element near the middle of his arrangement.
He wanted to show that properties come back again and again (they are periodic). A flat straight line cannot show this repeat. By coiling the line around a cylinder, every full turn brings you back to the same side, so similar elements line up one below the other. This was a clever way to show repeating properties before Mendeleev made his flat table.
Atomic weight (also called atomic mass). Atomic number was not known in 1862. He arranged elements in order of increasing atomic weight. For NEET, remember: all early scientists (Dobereiner, de Chancourtois, Newlands, Mendeleev) used atomic weight. Only Moseley later showed atomic number is the true basis.
No. NCERT says it 'did not attract much attention.' His paper was hard to understand and the diagram was confusing, so other chemists mostly ignored it. This is why Mendeleev usually gets the credit, even though de Chancourtois came first. For NEET, know that he was the FIRST to show periodicity, but his work was overlooked.
De Chancourtois came first, in 1862. John Newlands proposed his Law of Octaves later, in 1865. The correct time order is: Dobereiner's Triads (1817), de Chancourtois telluric helix (1862), Newlands' Octaves (1865), then Lothar Meyer and Mendeleev. Learning this order is a common NEET question.
Both used increasing atomic weight. De Chancourtois used a 3D spiral on a cylinder, and similar elements fell on the same vertical line. Newlands used a flat list and said every eighth element repeats properties (like musical octaves). The helix was a spiral shape; octaves was a counting rule.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
A.E.B. de Chancourtois, a French geologist, proposed it in 1862.
The name comes from tellurium, an element placed near the centre of his spiral arrangement. 'Telluric' relates to tellurium/earth.
Yes. It was the first arrangement to show that element properties repeat periodically when elements are ordered by increasing atomic weight.
His work was published in a confusing way and did not attract attention. Mendeleev later published a clear periodic table and the Periodic Law, so he gets the main credit.
Yes, but only as history. NEET can ask who made the first periodic arrangement, the year (1862), and that it used atomic weight on a cylinder/spiral.
