By Robert M. Hazen, Ph.D., George Mason University
The nature of chemical elements themselves is very complicated. Long before the existence of atoms had been proven, there were still chemical researchers all over the world looking to find useful compounds. And some of the substances they found appeared to be more fundamental than others. These ‘elements’ could not be broken down into other substances by any normal physical or chemical means.
Chemical Elements Known the Most
Many people might know that water can be decomposed with an electric current. And it breaks down into two gases—hydrogen and oxygen. But no matter what is done, it doesn’t seem possible to break down hydrogen and oxygen into simpler compounds. They seem to be more fundamental. They are chemical elements.
Ancient cultures knew of at least ten different chemical elements. Most of these were found in their native state, most of them were found as metals. There are precious metals such as copper, silver, and gold. They’re common enough to be noticed; they’re hard enough to be useful; they’re rare enough to be valued.
Platinum is a precious metal as well. Interestingly, platinum was not recognized in Europe or Asia, but it was used by pre-Columbian peoples in the New World, partly because platinum nuggets could be found in the streambeds of parts of South America.
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Naturally-occurring Chemical Elements
Other metals are also found rarely as native elements under unusual circumstances. There is iron, found as meteorites. Small quantities of lead, small amounts of mercury can be found in certain types of places. And so those also occur uncombined in nature; those are also naturally occurring elements. These metals, along with tin and antimony, could be produced in a fire from just common ores.
Indeed, some of these elements may have been discovered by accident. An ore just drops into a fire, and a little bit of this metal, antimony or tin, might have come out in that way. There are also nonmetallic elements that occur in nature. Carbon comes from charcoal and sulfur from volcanoes. Beautiful yellow sulfur crystals can be found near the mouths of some volcanoes. All these elements, by the way, are still mined in large quantities today.
Learn more about the chemistry of carbon.
Period of Alchemy and the Discovery of Chemical Elements
From the 12th century through to the 16th century was the period of alchemy, where various scholars learned to separate a few other elements by using intense fires. The new elements discovered during this period include arsenic and zinc, bismuth, and phosphorus. Between 1735 and 1805, chemists devised new techniques to purify and characterize more than two dozen new elements. This research went hand in hand with advances in mineralogy.
Many of the new elements were discovered by studying minerals through wet chemical analysis, where the minerals were dissolved or broken apart, or by blowpipe analysis, where an intensely hot flame was used to melt and fuse various parts of the minerals. And once in a while, a new element would come to light in that way.
The important elements—nickel, cobalt, magnesium, chromium, molybdenum, tungsten, uranium— were all discovered during this period. Also, during this period was the first isolation of gaseous elements. Hydrogen, nitrogen, and oxygen—all of them were isolated between 1772 and 1774.
Learn more about the states of matter and changes of state.
Joseph Priestley and the Dramatic Discovery of Oxygen
The most dramatic of these discoveries were made by the British chemist Joseph Priestley, who lived from 1733 to 1804. It was in the year 1774 that Priestley subjected mercury oxide, or HgO, a common mineral that can be collected off the surface of the Earth.
He subjected it to a temperature of about 450 degrees centigrade, and that resulted in a puddle of mercury forming at the bottom of his vial and releasing a gas, which turned out to be oxygen.
He collected that gas oxygen in his containers, and he found that this is the gas that’s essential for all burning processes. Indeed, he wrote, “What surprised me more than I can well express was that a candle burned in the air with a remarkably brilliant flame.” So he had discovered a pure source of oxygen.
The Use of Battery to Discover New Chemical Elements
The battery provided an important new technique called electrolysis. And by this technique of electrolysis, new elements can be produced and isolated. The battery was invented by Luigi Galvani, who placed an alternating sequence of plates—for example, zinc, silver, zinc, silver—in an acid bath to get an electric potential.
Electrolysis works like this: a chemical compound is dissolved in an acid bath, and then that acid bath is subjected to the electrical current. These alternating plates of metal create a positive electrode and a negative electrode.
Metals are often deposited on the negative side, on the anode side, while nonmetals concentrate on the cathode, the positive side, of this acid bath. And this way, new elements can be isolated, one going to each of the two electrodes in some cases.
The use of the battery to discover new elements began in 1797. The British chemist Sir Humphry Davy was a great lecturer in London. He used increasingly powerful batteries to separate potassium and sodium, boron, calcium, barium, cadmium—all very important elements that were separated and isolated for the first time by Davy using his battery.
Common Questions about the Concept of Chemical Elements
Chemical elements are basic substances in nature discovered by researchers before the existence of atoms had been proven. These ‘elements’ could not be broken down into other substances by any normal physical or chemical means.
Oxygen, among the most well-known chemical elements, was first discovered by chemist Joseph Priestley. He was able to extract pure oxygen from the mineral mercury oxide.
Sir Humphrey Davy was a British chemist who discovered numerous chemical elements such as calcium, barium, cadmium, sodium, and potassium using batteries which provide a technique called electrolysis.
