Periodic Table

The Development of the Periodic Table

DMITRI MENDELEEV

1834 – 1907

Mendeleev

This podcast recounts the remarkable life of Dmitri Mendeleev, highlighting his impoverished beginnings and his mother’s pivotal role in securing his education. It details his determined and somewhat difficult personality alongside his deep scientific curiosity about the 63 known elements. The text explains his breakthrough in creating the periodic table after a visionary dream, emphasising its revolutionary predictive power regarding undiscovered elements. Ultimately, the source portrays Mendeleev’s work as a triumph of perseverance and imagination, solidifying his enduring legacy in the scientific world and chemistry education.

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script

QUESTIONS

The Development of the Periodic Table

JOHN DALTON (1803)

Understand the Development of the Periodic Table

Describe how the periodic table was developed over time, including the contributions of scientists like Dmitri Mendeleev.
Explain how Mendeleev organised the elements and predicted the existence of undiscovered elements.

John Dalton (1803)

I proposed the atomic theory, suggesting that each element is made of unique atoms with specific weights. This laid the groundwork for organising elements by atomic weight.

Johann Döbereiner (1817)

I noticed that some elements could be grouped into “triads” (e.g., chlorine, bromine, iodine) based on similar properties and atomic weights.

John Newlands (1864)

John Newlands arranged elements based on their increasing atomic weights, similar to Dmitri Mendeleev; however, the key difference is that Newlands rigidly followed this order, grouping elements into “octaves” (every eighth element having similar properties), while Mendeleev prioritized chemical properties and was willing to switch elements in the sequence if it better aligned with their characteristics, even leaving gaps in his table to accommodate undiscovered elements with predicted properties; making his arrangement more flexible and predictive than Newlands’ “Law of Octaves.”

Alexandre-Émile Béguyer de Chancourtois (1862)

Created the telluric screw, a 3D arrangement of elements by atomic weight. Although innovative, it was difficult to use and gained little attention.

Dmitri Mendeleev (1869)

I made the breakthrough!

I wrote the names and properties of the 63 known elements on individual cards.

I was more flexible than Newlands arranging elements by increasing atomic weight and grouping elements with similar properties.

I also left gaps for undiscovered elements, predicting their properties with remarkable accuracy (e.g., gallium, germanium).

Dmitri Mendeleev (1869)

I organised the elements into rows (periods) and columns (groups).

The elements in the same group had similar chemical properties.

I left gaps in the table hinted at undiscovered elements, which were later found and matched my predictions.

Key Contributions of Mendeleev

Prediction of New Elements: Mendeleev’s gaps and predictions (e.g., gallium, scandium, germanium) were later confirmed, proving the table’s accuracy.
Organisation by Properties: He grouped elements with similar properties, such as alkali metals (Group 1) and halogens (Group 7), making it easier to study their behaviour.
Legacy: Mendeleev’s periodic table became the foundation of modern chemistry and is still used today.

Julius Lothar Meyer (1868)

I developed a similar table, organising elements by atomic weight and valency. However, my work was published after Mendeleev’s and received less recognition.

Henry Moseley (1913)

I discovered the concept of atomic number (the number of protons in an atom’s nucleus). This replaced atomic weight as the basis for organising the periodic table, resolving inconsistencies in Mendeleev’s table (e.g., the positions of iodine and tellurium).