Who is the father of the periodic table

It's hard to imagine today, but when scientists introduced the periodic table, it was merely a conjecture. It had to fight for attention and defend itself against attacks, and could easily have been abandoned. In fact, the table faced its first big test less than a decade after Dmitri Mendeleev produced his famous table in 1869. The element in question was gallium.

Mendeleev didn't discover the periodic nature of elements by himself—at least five other scientists also suggested that, if you arranged the elements by increasing weight, certain properties would reappear at regular intervals.   And Mendeleev's first table didn't look like the one we know today—it was flipped sideways, with rows for columns and columns for rows; someone else suggested he rotate it. But Mendeleev earned his place in history as the father of the periodic table for good reason: He incorporated more elements than anyone had before and did a better job of putting them in their proper spots.

Mendeleev also did something special with the gaps on the table. All the early periodic tables had holes where no known element fit. We know today they simply hadn't been discovered yet. But that wasn't necessarily obvious back then—perhaps they didn't exist, or perhaps the theory behind the periodic table wasn't true. Mendeleev, however, not only predicted that new elements would be discovered and that they would support his periodic system; he also had the audacity to predict the properties of undiscovered elements. One of his predictions concerned the ghost element below aluminum, which Mendeleev named eka-aluminum, using the Sanskrit word for "beyond." When a French aristocrat discovered eka-aluminum in 1875, Mendeleev tried to claim part of the credit. After all, he'd predicted it.

The aristocrat, Paul Emile François Lecoq de Boisbaudran, refused to let Mendeleev horn in on his discovery, however, and the two began to argue in papers in scientific journals. Lecoq de Boisbaudran first claimed that he'd never heard of Mendeleev's system, and later argued that Mendeleev had stolen the system anyway from an obscure French scientist who also had seen a glimmer of periodicity in the elements. For his part, Mendeleev picked apart Lecoq de Boisbaudran's data on the new element (soon named gallium). Mendeleev claimed, largely without evidence, that the accomplished Lecoq de Boisbaudran must have made mistakes when measuring gallium's weight and density, since they differed from Mendeleev's predictions.

The chutzpah here is incredible, but Mendeleev tended to trust his own instincts and formulas over mere evidence. Crackpots often do. The difference between Mendeleev and most crackpots is that Mendeleev was right: Lecoq de Boisbaudran soon had to publish an embarrassing retraction about gallium's weight and density, changing them to values that vindicated Mendeleev. According to science philosopher and historian Eric Scerri, "The scientific world was astounded to note that Mendeleev, the theorist, had seen the properties of a new element more clearly than the chemist who had discovered it."

This wasn't the only early trial that the periodic table faced. But the incorporation of the new element gallium was the first, and it helped prove the table wasn't just a clever but misleading arrangement of elements. It was a scientific tool with real predictive powers, something that could help scientists find new elements and refine what they knew about others. They could no longer ignore this powerful way to understand and organize the elements that make up the universe.

Internet search giant Google has dedicated a Doodle to Russian chemist Dmitri Mendeleev on his 182nd birth anniversary. Born on February 8, 1834, Mendeleev is popularly known as the "Father of Periodic Table".

He formulated the Periodic Law, created a farsighted version of the periodic table of elements, and used it to correct the properties of some already discovered elements and also to predict the properties of eight elements yet to be discovered.

Mendeleev's table, published in 1869, correctly organised the 56 known elements based on their atomic mass. While some of Mendeleev's predictions were not accurate, he did give to the world the foundations of the Periodic Table that is used in classrooms worldwide today with some new additions.

The table was expanded and refined over the years with further discoveries. Its seventh row was finally completed in January -- just weeks ahead of Mendeleev's birth anniversary.

While Google's final doodle shows the master himself with his vision of the Periodic Table, thanks to artist Robinson Wood who imagines Mendeleev in the act of setting down the logic of his table. There were other doodle ideas that did not make it. One of them shows Mendeleev with the element that he named after himself, Mendelevium (atomic number 101). Another illustration that did not make it to the final one, shows Mendeleev's famous desk where he was often photographed.

With inputs from IANS

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Mendeleev’s table had left some notable gaps, such as the spaces just below aluminum and just below silicon. Mendeleev took the bold step to predict that new elements would one day be discovered and placed into the empty spaces below aluminum and silicon. 

He even went so far as to propose temporary names for these elements. He invoked the prefix ‘eka’ from the Sanskrit word meaning ‘first’, calling them ‘eka-aluminum’ and ‘eka-silicon’ for the ‘first’ element below aluminum and the ‘first’ element below silicon.

His predictions came under a certain amount of criticism, both for a lack of supporting scientific evidence and the apparent brashness of proposing to name an element that he had not himself discovered—even if it was meant to be a temporary name.

Mendeleev: The Father of the Periodic Table

However, Mendeleev’s critics were silenced in short order. In 1875, eka-aluminum was discovered in Paris, France, where it was re-named gallium, in honor of France’s Gallic heritage. Reinforcing Mendeleev’s prediction, the new element was discovered hiding in a sample of zinc ore, which is the element just to its left in Mendeleev’s table. Moreover, gallium’s atomic mass and bonding characteristics perfectly matched Mendeleev’s predictions for eka-aluminum.

Further vindication came a decade later, in 1886 when eka-silicon was discovered in Germany and promptly named germanium.

These two discoveries and others like them verified Mendeleev’s predictions and ultimately cemented his legacy as the father of the periodic table.

Henry Moseley

In a sense, one might think of Mendeleev as the grandfather of the periodic table, as there is a more direct father of the modern periodic table, Henry Moseley.

Moseley is the scientist most directly responsible for realizing that the structure of the atom is key to understanding the elements themselves. It is the number of protons in the nucleus of an atom that determines the identity of each element, and not the atomic mass.

Organizing elements by atomic mass had seemed to produce a meaningful table, but that was only because the atomic mass of elements is closely connected to the real property that drives periodic trends—the atomic number.

It was something of a happy accident that atomic mass and atomic number trend quite similarly. But the trends are not identical. This is why Mendeleev could never explain hiccups in the trend: Nickel is lower in mass than cobalt; tellurium is higher in mass than iodine.

Mendeleev often wrote these off to inaccurate atomic mass measurements, assuming that newer technology and better techniques would eventually correct the issue. However, advancing technology would actually prove those atomic mass values to be correct. It would also reveal the true nature of the atom.

This article comes directly from content in the video series Understanding the Periodic Table. Watch it now, on Wondrium.

Understanding the Atomic Structure

Moseley’s new understanding of the periodic table was based on recent discoveries that suggested atoms were made of small, subatomic particles.

Moseley was a student of another great scientist, Earnest Rutherford, who himself discovered the atomic nucleus, proving that negatively charged electrons orbit a compact, positively charged nucleus. 

Moseley was a brilliant young researcher, keen on carrying on with the research that his mentor had conducted. So, he developed a special method of determining the charge of an atom’s nucleus using x-ray radiation. He applied his x-ray technique to measure the integer charge on elemental nuclei, and ordered the elements based on that number, rather than using atomic mass. When he did this, tellurium fell perfectly into place before iodine, and nickel fell perfectly into place before cobalt.

At the age of 26, Moseley had solved the riddle that had plagued Mendeleev’s table for more than 40 years.

Moseley’s contribution to our understanding of atomic structure is enormous. He finally made it possible to justify the correct ordering of the elements in the table. It was the atomic number, not the atomic mass, that mattered.

And yet, Moseley’s name is rarely invoked in discussions of the table. No element is named in his honor. These oversights seem largely due to Moseley’s untimely death, just one year later, at the age of 27. Against the advice of his mentors, in 1915 he enlisted in the British military and was killed in action during the ill-fated battle of Gallipoli.

Common Questions about Dmitri Mendeleev and Henry Moseley

Q: Why is Dmitri Mendeleev regarded as the father of the periodic table?

In his periodic table, Mendeleev had left some notable gaps, such as the spaces just below aluminum and silicon. These gaps were meant for yet-to-be-discovered elements. When those elements were discovered later, it was found out that the properties of the new elements matched Mendeleev’s predictions. This cemented his legacy as the father of the periodic table.

Q: Who was Henry Moseley?

Henry Moseley is the scientist most directly responsible for realizing that the structure of the atom is key to understanding the elements themselves; it is the number of protons in the nucleus of an atom that determines the identity of each element, and not the atomic mass.

Q: How did Henry Moseley solve the riddle of Mendeleev’s periodic table?

Moseley developed a special method of determining the charge of an atom’s nucleus using x-ray radiation. He applied his x-ray technique to measure the integer charge on elemental nuclei, and ordered the elements based on that number, rather than using atomic mass. When he did this, tellurium fell perfectly into place before iodine, and nickel fell perfectly into place before cobalt. He, thus, solved the riddle that had plagued Mendeleev’s table for more than 40 years.

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