Elements With Color Names

During chemical reactions preceding the discovery of an element, chemists have often observed the characteristic color of an element or its mineral and have sometimes seen with astonishment the variety of colors that an individual element can have. Sometimes the typical colors of the element s spectral lines have been emphasized. These circumstances have dictated that many elements have names that express their color and color variations (Table 3.14). 

Indium Indigo Latin The blue color indigo 

Praseodymium Prasios didymos Greek Green twin 

---

The existence of these different practices was not sufficient to create a discipline or subdiscipline of physical chemistry, but it showed the way. One definition of physical chemistry is that it is the application of the techniques and theories of physics to the study of chemical reactions, and the study of the interrelations of chemical and physical properties. That would mean that Faraday was a physical chemist when engaged in electrolytic researches. Other chemists devised other essentially physical instruments and applied them to chemical subjects. Robert Bunsen (1811—99) is best known today for the gas burner that bears his name, the Bunsen burner, a standard laboratory instrument. He also devised improved electrical batteries that enabled him to isolate new metals and to add to the list of elements. Bunsen and the physicist Gustav Kirchhoff (1824—87) invented a spectroscope to examine the colors of flames (see Chapter 13). They used it in chemical analysis, to detect minute quantities of elements. With it they discovered the metal cesium by the characteristic two blue lines in its spectrum and rubidium by its two red lines. We have seen how Van t Hoff and Le Bel used optical activity, the rotation of the plane of polarized light (detected by using a polarimeter) to identify optical or stereoisomers. Clearly there was a connection between physical and chemical properties. 

Phosphoms exists in at least three allotropic forms. Allotropes are forms of an element with different physical and chemical properties. The three main allotropes are named for their colors white phosphorus (also called yellow phosphorus), red phosphorus, and black phosphorus (also called violet phosphorus). These allotropes have different physical and chemical properties. 

Table 5.4 shows the chemical names of some transition element ions. When you do Practice Problems 5 and 6, you will become familiar with these names. Note in the photos accompanying the table that the different ions of a transition element often form compounds of different colors. 

Matter can be broadly classified into three types—elements, compounds, and mixtures. An element is the simplest type of matter with unique physical and chemical properties. An element consists of only one kind of atom. Therefore, it cannot be broken down into a simpler type of matter by any physical or chemical methods. An element is one kind of pure substance (or just substance), matter whose composition is fixed. Each element has a name, such as silicon, oxygen, or copper. A sample of silicon contains only silicon atoms. A key point to remember is that the macroscopic properties of a piece of silicon, such as color, density, and combustibility, are different from those of a piece of copper because silicon atoms are different from copper atoms in other words, each element is unique because the properties of its atoms are unique. 

Marignac investigated erbium precipitates and found that they were not homogeneous. Two elements were present. One formed red salts with a characteristic absorption spectrum, while compounds of the other element were colorless. The element with the red color kept the name erbium, the other he called ytterbium. The discovery was made in 1878 and separation was possible by addition of hyposulfurous acid to chloride solutions. The erbium precipitated but not the ytterbium. The two elements erbium and ytterbium also appeared to be mixed, and research had to continue. 

Shiny silvery metal that is relatively soft in its pure form. Forms a highly resistant oxide coat. Used mainly in alloys, for example, in construction steel. Tiny amounts, in combination with other elements such as chromium, makes steel rustproof and improves its mechanical properties. Highly suited for tools and all types of machine parts. Also applied in airplane turbines. Chemically speaking, the element is of interest for catalysis (for example, removal of nitric oxides from waste gases). Vanadium forms countless beautiful, colored compounds (see Name). Essential for some organisms. Thus, natural oil, which was formed from marine life forms, contains substantial unwanted traces of vanadium that need to be removed. 

Native copper has a distinctive reddish/brown color. Its first oxidation state (+1) forms compounds with copper ions named cuprous, also referred to as copper(I), and these ions are easily oxidized with elements in group 16 (e.g., oxygen and sulfur) and elements in group 17 (the halogens). 

Iridium and its parmer osmium were discovered in 1803 by the Enghsh chemist Smithson Tennant (1761-1815). In essence, he employed the same technique to separate these elements from platinum ores that is used today to pmify iridium. He dissolved the minerals with aqua regia, which left a black residue that looked much like graphite. After analyzing this shiny black residue, he identified two new elements—Ir and Os. Tennant was responsible for naming iridium after the Latin word iris because of the element s rainbow of colors. 

Si02 is one of the most abundant compounds in nature. It forms a number of minerals and several varieties whose names are quite familiar agate, car-nelian, sard, amethyst, chalcedony, flint, and chert. All are composed of Si02 with only small or trace amounts of other elements or compounds included during crystallization. In many cases it is the additional components that impart the peculiar color, optical, or physical properties to these minerals. The names are familiar because since ancient times these minerals were used or commonly set in jewelry. All of the names are varieties of the mineral quartz, the stable form of SiOj, formed at ordinary temperatures and pressures. Si02 also forms several polymorphs, which are mentioned below. 

---