By Ron B. Davis Jr., Georgetown University
The elements, carbon, sulfur, and phosphorus, are sometimes collectively referred to as the polyatomic nonmetals. Unlike oxygen and nitrogen, they prefer to form larger, more complex elemental molecules using many atoms of the same element—polyatomic. With this tendency to form more complex molecules comes some amazingly versatile chemistry exploited by technology which becomes clear when we consider the reactivity of these elements.
Discovery of Carbon and Sulfur
Carbon and sulfur are substances that have been known since ancient times. This is because their elemental forms do occur in nature and discovering them was likely as simple as happening upon a sample.
They took their rightful place on the list of elements in the 1700s, when Antoine Lavoisier convinced the rest of the scientific community to begin looking at them as elements.
Discovery of Phosphorus
Phosphorus got an early start as well, although it was not discovered in nature as a pure material. Instead, the very first samples of phosphorus were obtained from an unlikely source, urine. In 1669 German physician Hennig Brandt was attempting to produce the fabled philosopher’s stone, a substance that alchemists believed could transmute less-valuable elements into gold.
In the process, he realized that it produced a solid substance that glowed, emitting light for long periods of time after it was isolated. He named his new substance phosphorus for the Greek terms meaning ‘light bringing’.
Once again, it was Lavoisier who realized a hundred years later that phosphorus was in fact an element, putting it in its rightful place as a fundamental type of matter.
Selenium’s Association with Sulfur
Selenium was discovered in 1817 by Jacob Berzelius, who noticed a red-brown sediment at the bottom of a sulfuric acid work.
Selenium’s Goldschmidt classification is a chalcophile, meaning it associates strongly with sulfur, the element just above.
This article comes directly from content in the video series Understanding the Periodic Table. Watch it now, on Wondrium.
Reaction with Oxygen
All four of our polyatomic nonmetals react readily with oxygen to form nonmetal oxides. Coal made from carbon burns to fuel powerplants and charcoal grills, releasing significant heat, but also carbon dioxide gas that contributes to the greenhouse effect.
Elemental sulfur can burn, though it is rarely an element that we burn on purpose since the resulting sulfur oxide gases are both toxic and a source of acid rain. It is the toxicity of its combustion products that made sulfur one of the world’s first chemical weapons.
Historical accounts describe ancient Greeks tossing flaming pitches mixed with sulfur over city walls to ‘encourage’ the inhabitants to surrender their city.
Sulfur oxide gases also form during the burning of sulfur-rich coal, which can be problematic. These sulfur oxide gases react with moisture in the air to form strong sulfuric acid which is carried back to the ground by precipitation.
This results in the infamous acid rain that caused environmental concerns in areas downwind of coal-fired powerplants around the world beginning in the 1970s and 80s.
The reaction between phosphorus and oxygen creates bright light and highly visible smoke of phosphorus pentoxide. This made phosphorus the material of choice for use in incendiary or tracer ammunition during the First World War.
Selenium’s oxide and sulfide compounds, by contrast, are valued simply for their ability to produce a brilliant red color when incorporated with glass.
Other Compounds of Carbon
There are many other compounds beyond simple oxides of these elements that rely heavily on these nonmetals for their specific properties and functions.
Carbon’s four-strong bonds make it ideal as a backbone chain for many useful polymers. Since only two bonds are needed to perpetuate a chain, each carbon atom is left with two additional bonds that can be exploited to functionalize the polymer.
Hydrogens can be attached to get high-density polyethylene used in rigid plastic containers. Moreover, adding a few carbon chains to those branches will get low-density polyethylene, a softer polymer used in plastic bags.
Switch those sites out for fluorine atoms to get the non-stick coating Teflon.
Or, alternate hydrogen and chlorine atoms to get polyvinylidene chloride—the original material from which Saran wrap was made.
Compounds for Sulfur and Selenium
Sulfur is also used in polymer production but in a different way. It does not form long chains the way carbon does, but its valence of two makes it ideal for cross-linking one polymer chain to another, as it does in vulcanized rubber.
The cross-links provided by sulfur add rigidity to the rubber product, making it an excellent material for the production of automobile tires.
Selenium, meanwhile, sometimes shows its metalloid side, as it can be alloyed with more common metals to enhance or change their properties. For example, selenium alloyed with bismuth can be substituted for lead in the production of brass.
Common Questions about the Reactivity of Carbon, Sulfur, and Phosphorus
Phosphorus was not discovered in nature as a pure material. Instead, the very first samples of phosphorus were obtained from an unlikely source, urine. In 1669 German physician Hennig Brandt was attempting an experiment during which he produced a solid substance that glowed, emitting light for long periods of time after it was isolated. He named his new substance phosphorus for the Greek terms meaning ‘light bringing’.
Elemental sulfur can burn, though it is rarely an element that we burn on purpose since the resulting sulfur oxide gases are both toxic and a source of acid rain. It is the toxicity of its combustion products that made sulfur one of the world’s first chemical weapons. Sulfur oxide gases also form during the burning of sulfur-rich coal. These sulfur oxide gases react with moisture in the air to form strong sulfuric acid.
The reaction between phosphorus and oxygen creates bright light and highly visible smoke of phosphorus pentoxide. This made phosphorus the material of choice for use in incendiary or tracer ammunition during the First World War.
