Dmitri Mendeleev

Chapter 1 · A Journey Across a Continent

Siberia, a burned glassworks, and a mother's determination

1834 – 1856 · Tobolsk · Moscow · St Petersburg

Dmitri Ivanovich Mendeleev was born on 8 February 1834 in Tobolsk, western Siberia, the youngest of a very large family — accounts differ on the number, but he had at least a dozen siblings. His father was a school headmaster who went blind the year Dmitri was born and lost his post.

His mother Maria took over a family glassworks and ran it to support the household — an extraordinary undertaking for a woman in provincial Russia. Dmitri watched glassmaking as a child, and it is often suggested this gave him his early feel for materials.

His father died in 1847 and the glassworks burned down in 1848. Maria then did something remarkable: convinced that her youngest son had unusual ability, she travelled with him across Russia — thousands of miles, much of it by horse-drawn cart — first to Moscow, where he was refused entry to the university because he was from Siberia, and then to St Petersburg, where his father's old connections secured him a place at the Main Pedagogical Institute in 1850. She died a few months later. He dedicated a later book to her memory, writing that she had taught by example and corrected with love.

He then developed tuberculosis and was sent south to Crimea to recover, teaching there and returning to St Petersburg in 1856 to take a master's degree.

A period in Heidelberg from 1859 gave him a laboratory of his own, and in 1860 he attended the Karlsruhe Congress, where Stanislao Cannizzaro's clarification of atomic weights settled years of confusion. Mendeleev later said it was decisive for him.

Why this matters

Reliable atomic weights, agreed at Karlsruhe in 1860, were the precondition for any periodic table — without them the elements could not be put in a meaningful order.

You have met the Siberian student. What would you ask him?

Ask Mendeleev

• “What did your mother do to get you an education?”
• “Why were you refused a place in Moscow?”
• “What did the Karlsruhe Congress settle?”
• “What did watching a glassworks teach you?”
• “How did you recover from tuberculosis and keep studying?”

Chapter 2 · 17 February 1869

A textbook problem, and a table drawn in a day

1867 – 1869 · St Petersburg

Mendeleev became professor of chemistry at St Petersburg in 1867 and set out to write a textbook, *Principles of Chemistry*, because no good Russian one existed. The problem was organisation: in what order should sixty-three known elements be presented?

He wrote the properties of each on cards — atomic weight, valence, the compounds it forms, its physical character — and arranged and rearranged them. Colleagues described him laying them out like a game of patience.

On 17 February 1869 by the Russian calendar he produced the arrangement. His own later account says the final scheme came to him in a dream, in which he saw a table where all the elements fell into place, and that he wrote it down on waking with only one correction needed. Whether or not the dream story is embellished — he told it decades afterwards — the working papers show months of systematic effort behind it.

His principle: arrange the elements in order of increasing atomic weight, and their properties recur periodically. Elements with similar chemical behaviour fall into the same vertical group.

Two decisions made his version different. Where the atomic weight order conflicted with chemical behaviour, he trusted the chemistry — placing tellurium before iodine, for instance, despite the weights suggesting otherwise. He was right, and the reason emerged decades later when Henry Moseley showed the true ordering principle is atomic number, the number of protons.

And he left gaps rather than forcing the sequence to be continuous.

Why this matters

Mendeleev's willingness to trust chemical behaviour over measured atomic weights meant his table was correct in places where the available data was wrong.

You have the table being made. What would you ask him?

Ask Mendeleev

• “How did writing a textbook lead to the periodic table?”
• “How much of the dream story is true?”
• “Why did you put tellurium before iodine?”
• “What does 'periodic' actually mean here?”
• “Why arrange the elements on cards?”

Chapter 3 · The Gaps

Describing three elements before anyone found them

1871 – 1886 · St Petersburg · Paris · Freiberg

Several chemists had spotted patterns among the elements. John Newlands proposed a law of octaves in 1865 and was mocked at a Chemical Society meeting, where a fellow was asked whether he had tried arranging them alphabetically. Lothar Meyer in Germany produced a table very similar to Mendeleev's at almost the same time.

What separated Mendeleev was the gaps. Rather than shuffle known elements to fill every position, he asserted that undiscovered elements existed and gave detailed predictions of their properties, using the Sanskrit prefix *eka* for 'one place below'.

For eka-aluminium he predicted an atomic weight around 68, a density of about 5.9, a low melting point, and that it would be discovered by spectroscopic analysis. In 1875 Paul-Émile Lecoq de Boisbaudran discovered gallium in France. Its properties matched — and when Boisbaudran's initial density measurement disagreed, Mendeleev wrote to say the sample must be impure. It was. On repurification, the density came out as he had predicted.

Eka-boron appeared in 1879 as scandium, found in Sweden.

Eka-silicon was the most striking. In 1886 Clemens Winkler in Germany isolated germanium, and its atomic weight, density, colour, oxide and chloride matched Mendeleev's 1871 predictions closely enough that Winkler described the correspondence as more than confirmation — as a demonstration that the periodic law had extended the scope of chemical vision.

After that, the table was not a proposal. It was a law.

“The properties of the elements are in periodic dependence upon their atomic weights.”

— Dmitri Mendeleev, statement of the periodic law, 1869 (translated from the Russian)

Why this matters

Mendeleev's predictions are a textbook example of what makes a scientific theory strong: it forecast specific, checkable facts that could have proved it wrong and did not.

You have the predictions confirmed. What would you ask him?

Ask Mendeleev

• “Why leave gaps instead of rearranging the elements?”
• “How could you describe an element nobody had seen?”
• “Why did you tell Boisbaudran his gallium sample was impure?”
• “How does your table differ from Lothar Meyer's?”
• “Why was Newlands laughed at for a similar idea?”

Chapter 4 · Balloons, Oil and Standards

A chemist who would not stay in the laboratory

1876 – 1907 · St Petersburg · Baku · Pennsylvania

Mendeleev's interests ran far beyond the table. He advised on the development of the Russian oil industry at Baku, travelling to Pennsylvania to study American methods, and argued that oil was too valuable as a chemical feedstock to burn as fuel — writing that burning petroleum was like heating a furnace with banknotes.

He worked on agriculture and fertilisers, promoted the Russian coal industry, and studied gases and solutions. In 1887 he made a solo balloon ascent to observe a solar eclipse, going up alone after deciding the aeronaut was too heavy, having never flown before.

From 1893 he directed Russia's Bureau of Weights and Measures, modernising the country's standards and introducing the metric system as an option.

The widely repeated claim that he set the strength of Russian vodka at forty per cent is a myth. His doctoral thesis was on the combination of alcohol and water, but it concerned solutions in general, and the forty per cent standard was fixed for taxation before his work.

He was politically outspoken and repeatedly clashed with the government. In 1890 he resigned his professorship after attempting to deliver a student petition to the minister of education.

His private life caused scandal. He divorced his first wife and married Anna Popova in 1882 before the Orthodox Church's required waiting period, making the marriage technically bigamous. The Tsar, asked to act, is reported to have replied that Mendeleev had two wives but Russia had only one Mendeleev.

In 1906 he was nominated for the Nobel Prize in Chemistry and lost by one vote on the committee. Svante Arrhenius, whose theory of ionic dissociation Mendeleev had criticised, is generally held to have campaigned against him. He died on 2 February 1907.

Why this matters

Mendeleev treated chemistry as a public resource — advising on oil, agriculture and weights and measures — which makes him an early model of the scientist as national adviser.

You have the public man. What would you ask him?

Ask Mendeleev

• “Why did you say burning oil was like burning banknotes?”
• “Did you really standardise vodka at forty per cent?”
• “Why go up in a balloon alone with no experience?”
• “Why did you resign your professorship in 1890?”
• “How did you lose the Nobel Prize by one vote?”

Chapter 5 · The Table Since

Noble gases, atomic number, and an element with his name

1894 and after

Mendeleev's table faced two serious tests after 1869, and it survived both.

The first was the discovery from 1894 of a whole family of elements he had not predicted at all — argon, helium, neon, krypton, xenon — which reacted with nothing and appeared to fit nowhere. Mendeleev was initially resistant, at one point suggesting argon might be a form of nitrogen. William Ramsay proposed that they formed an entirely new group, and when they were added as a column between the halogens and the alkali metals, the periodicity held perfectly. A table that can absorb an unexpected family without breaking is a strong table.

The second was the explanation. Mendeleev had ordered elements by atomic weight and had to break his own rule occasionally. In 1913 Henry Moseley, using X-ray spectra, showed the true ordering principle is atomic number — the number of protons in the nucleus — which resolved every anomaly at once. Moseley was killed at Gallipoli two years later, aged twenty-seven.

Quantum mechanics then explained why periodicity exists: the recurring properties follow from the arrangement of electrons in shells, and the groups correspond to the outer electron configuration.

Mendeleev did not know about protons, electrons or nuclei. He found the pattern from chemical behaviour alone, and the pattern turned out to be a consequence of atomic structure nobody would understand for fifty years.

Element 101, synthesised in 1955, is mendelevium. The periodic table now hangs in essentially every chemistry classroom in the world, and 2019 was declared its international year.

Why this matters

The periodic table is the single most useful organising device in the physical sciences: it lets a chemist predict how an unfamiliar element will behave from its position alone.

You have the table's later history. What would you ask him?

Ask Mendeleev

• “Why did the noble gases nearly break your table?”
• “What did Moseley's atomic number explain?”
• “How could you find the pattern without knowing about electrons?”
• “What does the table let a chemist do today?”
• “How would you feel about an element named after you?”

What Mendeleev changed

The periodic table organises all chemical knowledge and lets chemists predict the behaviour of unfamiliar elements from position alone. Mendeleev's successful predictions of gallium, scandium and germanium established the periodic law as one of the strongest examples of a testable and confirmed scientific theory.

A debate that continues

Historians of chemistry weigh Mendeleev's contribution against Lothar Meyer's near-simultaneous table and earlier attempts by Newlands and de Chancourtois, generally concluding that the predictions rather than the arrangement alone are what made his version decisive.

Keep exploring — ask Mendeleev

• “How do you decide when to trust a pattern over a measurement?”
• “What did you expect would be found in the gaps you left?”
• “What else did you want Russian science to achieve?”

Related lives

• Niels Bohr — Architect of the Quantum Atom
• Marie Curie — Two-Time Nobel Laureate
• Louis Pasteur — Father of Germ Theory

Related themes

The periodic table and atomic structure · Elements and compounds · Prediction and scientific theory