By Ron B. Davis Jr., Georgetown University
The first column of the periodic table is a special place. It contains hydrogen, the granddaddy of all elements, at the top of the group. Except for hydrogen, which was first isolated in the 1600s and identified as an element in the 1700s, all of the other elements from this group evaded detection until at least the 19th century.
Elements That Were Easy to Find
By the start of the 1800s, about thirty elements in all had been discovered, about one-third of all the naturally occurring elements. Iron, gold, silver, mercury, tin, lead, carbon, and sulfur had been known since ancient times. Many additional elements like nitrogen, oxygen, chlorine, and phosphorus had also been discovered and isolated in their elemental forms by then. At least one representative from every row of the table had been discovered as well.
But, in the midst of all this discovery, what’s remarkable is that group 1 elements, apart from hydrogen, had not yet been discovered. Sodium and potassium together make up nearly 5% of the Earth’s crust, yet they were unknown.
Even lithium, the third lightest of all the elements and one of only three that were created during the Big Bang, had evaded detection and isolation by an ever-growing cadre of curious and observant scientists. But as the 19th century dawned, half of the members of this group would be discovered within a single decade.
A Magical Battery
In an interesting twist, it was two other well-known elements—copper and zinc—that would make it possible for one very ambitious young chemist to turn the contents of his fireplace into two of the most recognizable elements on the table.
In 1799, Alessandro Volta, an Italian physicist, built a curious-looking contraption made principally of copper and zinc discs stacked in an alternating pattern. Volta had reasoned that placing different metals in contact with one another could produce a fight over electrons that would produce an electrochemical potential.
When properly assembled and soaked with acid, his pile of alternating copper and zinc plates did, indeed, produce an electrical voltage. His creation was later named ‘the voltaic pile’, but we know it better today as an electrical battery—the first of the modern scientific era. It was this electrical battery, in the right hands, that opened the door to discovering the alkali metals.
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And those hands belonged to a young scientific prodigy by the name of Humphry Davy, a British chemist and inventor born in Cornwall in 1778 to a middle-class family. He was barely in his twenties when Volta’s creation hit the scientific scene, and Davy quickly discovered that he could use a battery to isolate two new elements, sodium and potassium from—of all things—wood ashes.
Davy collected wood ashes from various sources, soaking them in water, then isolating the resulting solid which was known as ‘caustic potash’ or ‘lye.’ Today we call this substance potassium hydroxide. After melting this product in a furnace, he then applied an electrical voltage across the sample using a voltaic pile.
Davy essentially used this new electrical battery to produce an electrochemical force capable of pushing that unwanted electron back onto the alkali metal ions in his molten caustic potash. At the negatively charged electrode, electrons were forced into the alkali metal ions by the electrical voltage provided by his voltaic pile. The result of this process is a shiny, soft metal that quickly, and rather vigorously, reacts with both oxygen and water to reform the oxide and hydroxide compounds from which it came.
Signs of lithium were first observed about a decade later in the line emission spectrum of a mineral called petalite. Once Davy was aware of the existence of this new element that behaved very similarly to sodium and potassium, he was quickly able to obtain small amounts of the pure element using his electrolysis technique. Lithium, sodium, and potassium had completed what would soon become one of Dobereiner’s famous triads.
Robert Bunsen’s Discovery
But the next two alkali metals in the group would have to wait much longer. Rubidium and cesium were not discovered until the 1860s, just in time to make it onto Mendeleev’s initial periodic table. Both of these elements were discovered by Robert Bunsen—yes, the burner is named for him.
Bunsen developed his special burner to create a hotter, less colored flame that would help him prospect for new elements’ line emission spectra. Two of the elements he discovered are named for the characteristic colors that they produced in his now-famous burner.
The rubidium spectrum is dominated by two ‘ruby’ red lines. Cesium has strong lines that are sky blue in color, similar to a bluish-gray that in Latin was called caesius—which is why the element itself is sometimes spelled cesium.
Then there’s francium. Francium is the undisputed king of elemental hide and seek, eluding Davy, Bunsen, and every other chemist for nearly another century. But interestingly, francium’s elusiveness isn’t tied to its reactivity. Francium simply has a nucleus that’s highly unstable and puts it in a class all its own.
Common Questions about the Discovery of the First Column Elements
‘The voltaic pile‘ is better known as the electrical battery today. It was invented by Alessandro Volta in 1799. He assembled alternating plates of copper and zinc in a specific way and soaked them in acid. The result was an electrical voltage. This invention was later used to discover other elements from the periodic table.
Humphry Davy needed a force strong enough to push the unwanted electron back onto the alkali metal ions in his molten caustic potash. He used an electrical battery to generate an electrochemical force capable of this. His electrical battery basically forced the electrons at the negatively charged electrode into the alkali metal ions. The result of this process was a shiny new metal and a new member of the periodic table.
Humphry Davy used a series of techniques to discover sodium and potassium and he later also discovered lithium. On the other hand, Robert Bunsen was responsible for two other elements in the periodic table: rubidium and cesium.