Lead is classified as one of the “other metals.” All of the other metals have qualities of malleability and ductility. They are similar to the transition elements, but do not have varying oxidation states, and their valence electrons only exist in their outer shells. The other metals are solid and dense. Lead, of period 6, group 14, is atomic number 82. Humans have been aware of lead since ancient times, and it has had and still has numerous uses today. Lead and its compounds are poisonous in large quantities as well as prolonged exposure to small quantities because it builds up in the body.
The ancient Greeks and Romans were very familiar with lead, but it is unknown who exactly discovered it. It has been mined for more than 6,000 years. It was originally known as “plumbum” to the Romans, which translated means “waterworks,” and it is also the origin of the word “plumbing.” Plumbum is the source of the atomic symbol, Pb. The Romans used lead to make their water pipes without being aware of the deadly heavy metal poisoning lead invariably causes. They distinguished two types of lead: black lead, or “plumbum nigrum,” and white lead, or “plumbum album,” which was actually tin. Tin is very similar to lead, as it is also one of the other metals and sits above lead on the periodic table. In addition to plumbing, lead was also used for statues, coins and eating utensils. The modern word lead is derived from the Anglo-Saxon word “lead,” simply meaning metal.
Lead is sometimes found free in nature, but is most often obtained from ores like galena (PbS), anglesite (PbSO4), cerussite (PbCO3), and minum (Pb3O4). Lead is separated from the ores by roasting them in hot air. There are thirty-five isotopes of lead, with mass numbers 181 to 215. Naturally occurring lead is composed of a mixture of the four most common isotopes: Pb-204, Pb-206, Pb-207 and Pb-208. Around one-third of the lead used in the United States comes from recycling previously used lead, rather than mining. When freshly cut, lead displays a bright shiny quality and a bluish-gray color. It tarnishes slowly in air to a dull gray.
The high density of lead makes it a good shield against X-ray and gamma radiation, so it is used in protective suits in the presence of X-ray machines and in nuclear reactors. Lead is used to line containers of corrosive liquids and also to protect wires from corrosion. It can be used to absorb sound vibrations and is also commonly used in the manufacture of ammunition.
The vast majority of lead is used in lead-acid storage batteries, like those found in automobiles, because it is a poor conductor of electricity. Solder is a common alloy of lead and tin. It has a low melting point and is used to join electrical and metal components. Type metal, made of lead, tin and antimony, is used to make plates for printing presses. There is also a number of lead compounds. Litharge (PbO) is used to make lead crystal and flint glass, which are involved in the hardening of rubber. Litharge also appeared in the infamous lead paints that were previously common and now illegal.
