Dmitri Mendeleev

Dmitri Mendleev

As he attempted to classify the elements according to their chemical properties, he noticed patterns that led him to postulate his periodic table; he claimed to have envisioned the complete arrangement of the elements in a dream: „I saw in a dream a table where all elements fell into place as required. Awakening, I immediately wrote it down on a piece of paper, only in one place did a correction later seem necessary.“

Though Mendeleev was widely honored by scientific organizations all over Europe, including (in 1882) the Davy Medal from the Royal Society of London (which later also awarded him the Copley Medal in 1905), he resigned from Saint Petersburg University on 17 August 1890. He was elected a Foreign Member of the Royal Society in 1892, and in 1893 he was appointed director of the Bureau of Weights and Measures, a post which he occupied until his death.

In 1905, Mendeleev was elected a member of the Royal Swedish Academy of Sciences. The following year the Nobel Committee for Chemistry recommended to the Swedish Academy to award the Nobel Prize in Chemistry for 1906 to Mendeleev for his discovery of the periodic system. The Chemistry Section of the Swedish Academy supported this recommendation.

The attempts to nominate Mendeleev in 1907 were again frustrated by the absolute opposition of Arrhenius.

In 1907, Mendeleev died at the age of 72 in Saint Petersburg from influenza. His last words were to his physician: “Doctor, you have science, I have faith,” which is possibly a Jules Verne quote.

*8 February 1834, Verkhnie Aremzyani, Tobolsk Governorate, Russian Empire

†2 February 1907, Saint Petersburg, Russian Empire

Dmitri Ivanovich Mendeleev was a Russian chemist and inventor. He is best remembered for formulating the Periodic Law and creating a farsighted version of the periodic table of elements. He used the Periodic Law not only to correct the then-accepted properties of some known elements, such as the valence and atomic weight of uranium, but also to predict the properties of three elements that were yet to be discovered.

Mendeleev was raised as an Orthodox Christian, his mother encouraging him to “patiently search divine and scientific truth”

At the age of 13, after the passing of his father and the destruction of his mother’s factory by fire, Mendeleev attended the Gymnasium in Tobolsk.

In 1849, his mother took Mendeleev across Russia from Siberia to Moscow with the aim of getting Mendeleev enrolled at the Moscow University. The university in Moscow did not accept him. The mother and son continued to Saint Petersburg to the father’s alma mater.

The now poor Mendeleev family relocated to Saint Petersburg, where he entered the Main Pedagogical Institute in 1850.

After graduation, he contracted tuberculosis, causing him to move to the Crimean Peninsula on the northern coast of the Black Sea in 1855. While there, he became a science master of the 1st Simferopol Gymnasium. In 1857, he returned to Saint Petersburg with fully restored health.

Between 1859 and 1861, he worked on the capillarity of liquids and the workings of the spectroscope in Heidelberg. Later in 1861, he published a textbook named Organic Chemistry. This won him the Demidov Prize of the Petersburg Academy of Sciences

Mendeleev became a professor at the Saint Petersburg Technological Institute and Saint Petersburg State University in 1864, and 1865, respectively. In 1865, he became Doctor of Science for his dissertation “On the Combinations of Water with Alcohol”.

He achieved tenure in 1867 at St. Petersburg University and started to teach inorganic chemistry, while succeeding Voskresenskii to this post; by 1871, he had transformed Saint Petersburg into an internationally recognized center for chemistry research.

After becoming a teacher in 1867, Mendeleev wrote the definitive textbook of his time: Principles of Chemistry. It was written as he was preparing a textbook for his course. This is when he made his most important discovery. 

Mario Molina

Mario Molina

In his career, Molina held research and teaching positions at University of California, Irvine, California Institute of Technology, Massachusetts Institute of Technology, University of California, San Diego, and the Center for Atmospheric Sciences at the Scripps Institution of Oceanography.

Molina was also Director of the Mario Molina Center for Energy and Environment in Mexico City. Molina was a climate policy advisor to the President of Mexico, Enrique Peña Nieto.

Molina was named by U.S. President Barack Obama to form a transition team on environmental issues in 2008. Under President Obama, he was a member of the United States President’s Council of Advisors on Science and Technology.

In 2020, Mario Molina contributed to research regarding the importance of wearing face masks amid the SARS-COV-2 pandemic.

On 7 October 2020, the National Autonomous University of Mexico announced that Molina had died of a heart attack.

*19 March 1943, Mexico City, Mexico

†7 October, 2020, Mexico City, Mexico

Mario José Molina-Pasquel Henríquez was a Mexican chemist. He played a pivotal role in the discovery of the Antarctic ozone hole, and was a co-recipient of the 1995 Nobel Prize in Chemistry for his role in discovering the threat to the Earth’s ozone layer from chlorofluorocarbon (CFC) gases.

He was the first Mexican-born scientist to receive a Nobel Prize in Chemistry and the third Mexican born person to receive the Nobel award.

Before deciding to become a research chemist, Mario Molina had considered the idea pursuing a musical career, in particular, becoming a violinist.

After completing his basic studies in Mexico City and attending boarding school at the Institut auf dem Rosenberg in Switzerland, he earned a bachelor’s degree in chemical engineering at the National Autonomous University of Mexico in 1965.

In 1967 he earned his postgraduate degree in polymerization kinetics at the Albert Ludwig University of Freiburg, West Germany, and in 1972 a Ph.D. in physical chemistry from the University of California, Berkeley, working with George C. Pimentel.

Between 1974 and 2004, Molina variously held research and teaching posts at University of California, Irvine, the Jet Propulsion Laboratory at Caltech, and the Massachusetts Institute of Technology, where he held a joint appointment in the Department of Earth Atmospheric and Planetary Sciences and the Department of Chemistry. 

On July 1, 2004, Molina joined the Department of Chemistry and Biochemistry at University of California, San Diego, and the Center for Atmospheric Sciences at the Scripps Institution of Oceanography.

Molina served on the board of trustees for Science Service, now known as Society for Science & the Public, from 2000 to 2005. He also served on the board of directors of the John D. and Catherine T. MacArthur Foundation (2004–2014), and as a member of the MacArthur Foundation’s Institutional Policy Committee and its Committee on Global Security and Sustainability.

Marie Curie

Marie Curie

While a French citizen, Marie Skłodowska Curie, who used both surnames, never lost her sense of Polish identity. She taught her daughters the Polish language and took them on visits to Poland. She named the first chemical element she discovered polonium, after her native country.

Marie Curie died in 1934, aged 66, at the Sancellemoz sanatorium in Passy , France, of aplastic anemia from exposure to radiation in the course of her scientific research and in the course of her radiological work at field hospitals during World War I.

In addition to her Nobel Prizes, she has received numerous other honours and tributes; in 1995 she became the first woman to be entombed on her own merits in Paris’ Panthéon, and Poland declared 2011 as the Year of Marie Curie during the International Year of Chemistry.

She is the subject of numerous biographical works, where she is also known as Madame Curie.

*7 November 1867, Warsaw, Congress Poland, Russian Empire

†4 July 1934, Passy, Haute-Savoie, France

Marie Salomea Skłodowska Curie was a Polish and naturalized-French physicist and chemist who conducted pioneering research on radioactivity.

As the first of the Curie family legacy of five Nobel Prizes, she was the first woman to win a Nobel Prize, the first person and the only woman to win the Nobel Prize twice, and the only person to win the Nobel Prize in two scientific fields. She was the first woman to become a professor at the University of Paris in 1906.

She was born in Warsaw, in what was then the Kingdom of Poland, part of the Russian Empire. She studied at Warsaw’s clandestine Flying University and began her practical scientific training in Warsaw.

In 1891, aged 24, she followed her elder sister Bronisława to study in Paris, where she earned her higher degrees and conducted her subsequent scientific work.

In 1895 she married the French physicist Pierre Curie, and she shared the 1903 Nobel Prize in Physics with him and with the physicist Henri Becquerel for their pioneering work developing the theory of “radioactivity”—a term she coined. In 1906 Pierre Curie died in a Paris street accident.

Marie won the 1911 Nobel Prize in Chemistry for her discovery of the elements polonium and radium, using techniques she invented for isolating radioactive isotopes.

Under her direction, the world’s first studies were conducted into the treatment of neoplasms by the use of radioactive isotopes. In 1920 she founded the Curie Institute in Paris, and in 1932 the Curie Institute in Warsaw; both remain major centres of medical research. During World War I she developed mobile radiography units to provide X-ray services to field hospitals.

Henry Cavendish

Henry Cavendish

In 1773, Henry joined his father as an elected trustee of the British Museum, to which he devoted a good deal of time and effort. Soon after the Royal Institution of Great Britain was established, Cavendish became a manager (1800) and took an active interest, especially in the laboratory, where he observed and helped in Humphry Davy’s chemical experiments.

 Cavendish published no books and few papers, but he achieved much. Several areas of research, including mechanics, optics, and magnetism, feature extensively in his manuscripts, but they scarcely feature in his published work.

In 1783, Cavendish published a paper on eudiometry (the measurement of the goodness of gases for breathing). He described a new eudiometer of his invention, with which he achieved the best results to date, using what in other hands had been the inexact method of measuring gases by weighing them.

Then, after a repetition of a 1781 experiment performed by Priestley, Cavendish published a paper on the production of pure water by burning hydrogen in “dephlogisticated air” (air in the process of combustion, now known to be oxygen).

In 1785, Cavendish investigated the composition of common (i.e. atmospheric) air, obtaining impressively accurate results. He conducted experiments in which hydrogen and ordinary air were combined in known ratios and then exploded with a spark of electricity.

Cavendish died at Clapham on 24 February 1810.

*10 October 1731, Nice, Kingdom of Sardinia
†24 February 1810, London, England, United Kingdom of Great Britain and Ireland

Henry Cavendish was an English natural philosopher, scientist, and an important experimental and theoretical chemist and physicist. He is noted for his discovery of hydrogen, which he termed “inflammable air”. He described the density of inflammable air, which formed water on combustion, in a 1766 paper, On Factitious Airs. Antoine Lavoisier later reproduced Cavendish’s experiment and gave the element its name.

A notoriously shy man, Cavendish was nonetheless distinguished for great accuracy and precision in his researches into the composition of atmospheric air, the properties of different gases, the synthesis of water, the law governing electrical attraction and repulsion, a mechanical theory of heat, and calculations of the density (and hence the mass) of the Earth. His experiment to measure the density of the Earth has come to be known as the Cavendish experiment.

From the age of 11 Henry attended Newcome’s School, a private school near London. At the age of 18 (on 24 November 1748) he entered the University of Cambridge in St Peter’s College, now known as Peterhouse, but left three years later on 23 February 1751 without taking a degree (at the time, a common practice). He then lived with his father in London, where he soon had his own laboratory.

In 1758, he took Henry to meetings of the Royal Society and also to dinners of the Royal Society Club. In 1760, Henry Cavendish was elected to both these groups, and he was assiduous in his attendance after that.

His interest and expertise in the use of scientific instruments led him to head a committee to review the Royal Society’s meteorological instruments and to help assess the instruments of the Royal Greenwich Observatory. His first paper, Factitious Airs, appeared in 1766.

Other committees on which he served included the committee of papers, which chose the papers for publication in the Philosophical Transactions of the Royal Society, and the committees for the transit of Venus (1769), for the gravitational attraction of mountains (1774), and for the scientific instructions for Constantine Phipps’s expedition (1773) in search of the North Pole and the Northwest Passage.

Amedeo Avogadro

Amadeo Avogadro

Eventually, King Charles Albert granted a Constitution (Statuto Albertino) in 1848. Well before this, Avogadro had been recalled to the university in Turin in 1833, where he taught for another twenty years.

He died on 9 July 1856.

The scientific community did not give great attention to Avogadro’s theory, and it was not immediately accepted. André-Marie Ampère proposed a very similar theory three years later (in his “On the Determination of Proportions in which Bodies Combine According to the Number and the Respective Disposition of the Molecules by Which Their Integral Particles Are Made”), but the same indifference was shown to his theory as well.

Only through studies by Charles Frédéric Gerhardt and Auguste Laurent on organic chemistry was it possible to demonstrate that Avogadro’s law explained why the same quantities of molecules in a gas have the same volume.

Unfortunately, related experiments with some inorganic substances showed seeming contradictions. This was finally resolved by Stanislao Cannizzaro, as announced at Karlsruhe Congress in 1860, four years after Avogadro’s death.

He explained that these exceptions were due to molecular dissociations at certain temperatures, and that Avogadro’s law determined not only molecular masses, but atomic masses as well.

*9 August 1776, Turin, Piedmont-Sardinia

†9 July 1856, Turin, Piedmont-Sardinia

Lorenzo Romano Amedeo Carlo Avogadro, Count of Quaregna and Cerreto was an Italian scientist, most noted for his contribution to molecular theory now known as Avogadro’s law, which states that equal volumes of gases under the same conditions of temperature and pressure will contain equal numbers of molecules.

In tribute to him, the number of elementary entities (atoms, molecules, ions or other particles) in 1 mole of a substance, 6.02214076×1023, is known as the Avogadro constant, one of the seven SI base units and represented by NA.

He graduated in ecclesiastical law at the late age of 20 and began to practice. Soon after, he dedicated himself to physics and mathematics, and in 1809 started teaching them at a liceo (high school) in Vercelli, where his family lived and had some property.

In 1811, he published an article with the title Essai d’une manière de déterminer les masses relatives des molécules élémentaires des corps, et les proportions selon lesquelles elles entrent dans ces combinaisons (“Essay on a manner of Determining the Relative Masses of the Elementary Molecules of Bodies and the Proportions by Which They Enter These Combinations”), which contains Avogadro’s hypothesis. Avogadro submitted this essay to Jean-Claude Delamétherie’s Journal de Physique, de Chimie et d’Histoire naturelle (“Journal of Physics, Chemistry and Natural History”).

In 1815, he published Mémoire sur les masses relatives des molécules des corps simples (“Note on the Relative Masses of Elementary Molecules, As a Follow-up to the Essay on the Same Subject, Published in the Journal of Physics, July 1811”) about gas densities.

In 1820, he became a professor of physics at the University of Turin. Turin was now the capital of the restored Savoyard Kingdom of Sardinia under Victor Emmanuel I.

Avogadro was active in the revolutionary movement of March 1821. As a result, he lost his chair in 1823 (or, as the university officially declared, it was “very glad to allow this interesting scientist to take a rest from heavy teaching duties, in order to be able to give better attention to his researches”).

Linus Pauling

Linus Pauling

Pauling also worked on the structures of biological molecules, and showed the importance of the alpha helix and beta sheet in protein secondary structure. Pauling’s approach combined methods and results from X-ray crystallography, molecular model building, and quantum chemistry.

His discoveries inspired the work of James Watson, Francis Crick, Maurice Wilkins and Rosalind Franklin on the structure of DNA, which in turn made it possible for geneticists to crack the DNA code of all organisms.

In his later years he promoted nuclear disarmament, as well as orthomolecular medicine, megavitamin therapy, and dietary supplements. None of his ideas concerning the medical usefulness of large doses of vitamins have gained much acceptance in the mainstream scientific community.

Pauling died of prostate cancer on August 19, 1994, at home in Big Sur, California. He was 93 years old.

*28 February 1901, Portland, Oregon, U.S.

†19 August 1994, Big Sur, California, U.S.

Linus Carl Pauling was an American chemist, biochemist, chemical engineer, peace activist, author, and educator. He published more than 1,200 papers and books, of which about 850 dealt with scientific topics.

In high school, Pauling conducted chemistry experiments by scavenging equipment and material from an abandoned steel plant. With an older friend, Lloyd Simon, Pauling set up Palmon Laboratories in Simon’s basement.

They approached local dairies offering to perform butterfat samplings at cheap prices but dairymen were wary of trusting two boys with the task, and the business ended in failure.

Pauling attributes his interest in becoming a chemist to being amazed by experiments conducted by a friend, Lloyd A. Jeffress, who had a small chemistry lab kit.

For his scientific work, Pauling was awarded the Nobel Prize in Chemistry in 1954. For his peace activism, he was awarded the Nobel Peace Prize in 1962. He is one of four people to have won more than one Nobel Prize.

Of these, he is the only person to have been awarded two unshared Nobel Prizes, and one of two people to be awarded Nobel Prizes in different fields, the other being Marie Curie.

Pauling was one of the founders of the fields of quantum chemistry and molecular biology. His contributions to the theory of the chemical bond include the concept of orbital hybridisation and the first accurate scale of electronegativities of the elements.

Dorothy Hodgkin

Dorothy Hodgkin

She was working with Bernal on the technique’s first application to the analysis of a biological substance, pepsin. The pepsin experiment is largely credited to Hodgkin, however she always made it clear that it was Bernal who initially took the photographs and gave her additional key insights. Her PhD was awarded in 1937 for research on X-ray crystallography and the chemistry of sterols.

In 1933 Hodgkin was awarded a research fellowship by Somerville College, and in 1934, she moved back to Oxford. The college appointed her its first fellow and tutor in chemistry in 1936, a post which she held until 1977.

In April 1953, together with Sydney Brenner, Jack Dunitz, Leslie Orgel, and Beryl M. Oughton, Hodgkin was one of the first people to travel from Oxford to Cambridge to see the model of the double helix structure of DNA, constructed by Francis Crick and James Watson, which was based on data and technique acquired by Maurice Wilkins and Rosalind Franklin.

Among her most influential discoveries are the confirmation of the structure of penicillin as previously surmised by Edward Abraham and Ernst Boris Chain; and the structure of vitamin B12, for which in 1964 she became the third woman to win the Nobel Prize in Chemistry. Hodgkin also elucidated the structure of insulin in 1969 after 35 years of work.

*12 May 1910, Cairo, Egypt

†29 July 1994, Ilmington, Warwickshire, England

Dorothy Mary Crowfoot Hodgkin was a Nobel Prize-winning British chemist who advanced the technique of X-ray crystallography to determine the structure of biomolecules, which became essential for structural biology.

In 1921 Hodgkin’s father entered her in the Sir John Leman Grammar School in Beccles, England, where she was one of two girls allowed to study chemistry.

In 1928, Hodgkin joined her parents at the archaeological site of Jerash, in present-day Jordan, where she documented the patterns of mosaics from multiple Byzantine-era Churches dated to the 5th-6th centuries. She finished the drawings as she started her studies in Oxford, while also conducting chemical analyses of glass tesserae from the same site.

Her attention to detail through the creation of precise scale drawings of these mosaics mirrors her subsequent work in recognising and documenting patterns in chemistry. Hodgkin developed a passion for chemistry from a young age, and her mother, a proficient botanist, fostered her interest in the sciences. On her 16th birthday her mother gave her a book on X-ray crystallography which helped her decide her future.

She was further encouraged by the chemist A.F. Joseph, a family friend who also worked in Sudan.

In 1928 at age 18 she entered Somerville College, Oxford, where she studied chemistry. She graduated in 1932 with a first-class honours degree, the third woman at this institution to achieve this distinction.

In the autumn of that year, she began studying for a PhD at Newnham College, Cambridge, under the supervision of John Desmond Bernal. It was then that she became aware of the potential of X-ray crystallography to determine the structure of proteins.

Antonie Lavoisier

Antonie Lavoisier

He attended lectures in the natural sciences. Lavoisier’s devotion and passion for chemistry were largely influenced by Étienne Condillac, a prominent French scholar of the 18th century.

His first chemical publication appeared in 1764. From 1763 to 1767, he studied geology under Jean-Étienne Guettard. In collaboration with Guettard, Lavoisier worked on a geological survey of Alsace-Lorraine in June 1767.

While Lavoisier is commonly known for his contributions to the sciences, he also dedicated a significant portion of his fortune and work toward benefitting the public.

Lavoisier was a humanitarian—he cared deeply about the people in his country and often concerned himself with improving the livelihood of the population by agriculture, industry, and the sciences.

Lavoisier was a powerful member of a number of aristocratic councils, and an administrator of the Ferme générale. The Ferme générale was one of the most hated components of the Ancien Régime because of the profits it took at the expense of the state, the secrecy of the terms of its contracts, and the violence of its armed agents.

All of these political and economic activities enabled him to fund his scientific research. At the height of the French Revolution, he was charged with tax fraud and selling adulterated tobacco, and was guillotined.

*26 August 1743, Paris, France

†8 May 1794 Paris, France

Antoine-Laurent de Lavoisier was a French nobleman and chemist who was central to the 18th-century chemical revolution and who had a large influence on both the history of chemistry and the history of biology.

It is generally accepted that Lavoisier’s great accomplishments in chemistry stem largely from his changing the science from a qualitative to a quantitative one. Lavoisier is most noted for his discovery of the role oxygen plays in combustion. He recognized and named oxygen (1778) and hydrogen (1783), and opposed the phlogiston theory.

During 1773 Lavoisier determined to review thoroughly the literature on air, particularly “fixed air,” and to repeat many of the experiments of other workers in the field. He published an account of this review in 1774 in a book entitled Opuscules physiques et chimiques (Physical and Chemical Essays).

In the spring of 1774, Lavoisier carried out experiments on the calcination of tin and lead in sealed vessels, the results of which conclusively confirmed that the increase in weight of metals in combustion was due to combination with air. But the question remained about whether it was in combination with common atmospheric air or with only a part of atmospheric air.

Lavoisier helped construct the metric system, wrote the first extensive list of elements, and helped to reform chemical nomenclature. He predicted the existence of silicon (1787) and discovered that, although matter may change its form or shape, its mass always remains the same.

Lavoisier’s education was filled with the ideals of the French Enlightenment of the time, and he was fascinated by Pierre Macquer’s dictionary of chemistry.

Fritz Haber

Fritz Haber

Haber is also considered the “father of chemical warfare” for his years of pioneering work developing and weaponizing chlorine and other poisonous gases during World War I, especially his actions during the Second Battle of Ypres.

Haber also helped to develop gas masks with adsorbent filters which could protect against such weapons.

In his studies of the effects of poison gas, Haber noted that exposure to a low concentration of a poisonous gas for a long time often had the same effect (death) as exposure to a high concentration for a short time. He formulated a simple mathematical relationship between the gas concentration and the necessary exposure time. This relationship became known as Haber’s rule.

In the 1920s, Haber searched exhaustively for a method to extract gold from sea water, and published a number of scientific papers on the subject.

After years of research, he concluded that the concentration of gold dissolved in sea water was much lower than those reported by earlier researchers, and that gold extraction from sea water was uneconomic.

Haber, along with Max Born, proposed the Born–Haber cycle as a method for evaluating the lattice energy of an ionic solid.

*9 December 1868. Breslau, Prussia (now Wrocław, Poland)

†29 January 1934, Basel, Switzerland

Fritz Haber was a German chemist who received the Nobel Prize in Chemistry in 1918 for his invention of the Haber–Bosch process, a method used in industry to synthesize ammonia from nitrogen gas and hydrogen gas. This invention is of importance for the large-scale synthesis of fertilizers and explosives.

It is estimated that two thirds of annual global food production uses nitrogen from the Haber–Bosch process, and that this supports nearly half the world population.

Haber then sought an academic appointment, first working as an independent assistant to Ludwig Knorr at the University of Jena between 1892 and 1894.

Knorr recommended Haber to Carl Engler, a chemistry professor at the University of Karlsruhe who was intensely interested in the chemical technology of dye and the dye industry, and the study of synthetic materials for textiles.

Engler referred Haber to a colleague in Karlsruhe, Hans Bunte, who made Haber an Assistent in 1894.

Bunte suggested that Haber examine the thermal decomposition of hydrocarbons. By making careful quantitative analyses, Haber was able to establish that “the thermal stability of the carbon-carbon bond is greater than that of the carbon-hydrogen bond in aromatic compounds and smaller in aliphatic compounds”, a classic result in the study of pyrolysis of hydrocarbons. This work became Haber’s habilitation thesis.

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