Chemical Nomenclature, Elements and Symbols Help
Before standard element symbols and the Periodic Table were invented, discussing matter was a guessing game. Early scientists located in laboratories far distant from each other and speaking different languages had problems communicating. Cultural and language differences had a big impact on the naming of elements.
Additionally, just as ancient words and phrases are no longer part of today’s spoken languages, like “thee” and “thou” of old English, some element names originated from seldom used languages. The ancient name for copper is cuprum , which is why the symbol for copper is Cu. Scientists, confused by outdated names, needed a standard method that everyone used.
Nicknames added to the confusion. For example, baking soda used to make breads rise is actually sodium bicarbonate, but most people don’t call it that. Battery acid, the liquid that allows electricity to be mysteriously generated in cars, is really sulfuric acid. Household laundry bleach is usually known as sodium hypochlorite by chemists. Or do you know anyone who says, “Please pass the sodium chloride,” at a meal?
Common names for elements don’t provide accurate descriptions of elemental components. In fact, there are so many compounds and combinations of chemicals that sometimes figuring out what someone is talking about takes longer than the experiment!
For thousands of years, people have known about the basic elements. They knew rocks were hard, water was liquid, and fog was a mist. They knew materials could be heated, packed down, frozen, and altered in different ways, while others could not. What they didn’t understand was how matter seemed to turn from one form into another. Rust was a mystery. Explanations, based more on ancient myth than science, provided a path to understanding.
As time went on, scientists began to concentrate on the study of individual elements, but they still had a problem. Because in different languages chemical elements were known by different names, scientists couldn’t always be sure they were talking about the same thing. Just as a traveler, not knowing the language, has problems in foreign countries asking directions or finding a hotel, early chemists had problems comparing results and analyzing compounds that no one seemed to recognize. For example, the element, iron, is called Eisen in German, Piombo in Italian, Olovo in Czech, and Fer in French. Scientists, too busy with their experiments to study languages, ran into trouble when they tried to communicate their findings to colleagues in other parts of the world. To give you an idea of the problem, Table 4.1 provides a sampling of element names in different languages.
It was obvious that some sort of common code or chemical nomenclature was needed.
Chemical nomenclature is the standardized system used to name chemical compounds.
Symbols, at first based on Latin words, were used as an elemental code because writing the full name was time consuming. The powerful insecticide dichlorodiphenyltrichloroethane, or DDT, is written as (C 6 H 4 Cl) 2 CHCCl 3 with Berzelius’ method. If it weren’t for this shorthand code so much time would be taken up writing the samples’ names that there wouldn’t be any time left to do the experiment!
Chemical shorthand becomes especially important when writing chemical reactions. The symbol for an element can be one letter as in carbon (C) and phosphorus (P), two letters as in strontium (Sr) and molybdenum (Mo), or three letters as in the more recent elements in the Periodic Table such as ununquadium (Uuq) and ununoctium (Uuo). Notice that when an element has more than a one letter shorthand name, only the first letter of the symbol name is capitalized.
In 1862, the French geologist Antoine Béguyer de Chancourtois made up a list of elements, arranged by increasing atomic weight. He is said to have wrapped the list, divided into 16 sections around a cylinder. After he had done this, he noticed that different sets of similar elements lined up. One of these groups, oxygen, sulfur, selenium, and tellurium, had a repeated pattern. The atomic weights of these elements are 16, 32, 79, and 128, all multiples of 16. This periodic repeat seemed to be part of a natural pattern that occurred regularly.
Atomic weight is not to be confused with atomic number . Atomic number is written as the superscript of an element on the Periodic Table, while the atomic weight is written as a subscript. The atomic weight of boron is 10.81 while its atomic number is 5.
Atomic number (Z) equals the number of protons in the nucleus of an atom.