is a lead weight a pure substance compound
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Elements are anything found on the periodic table. As long as the matter is comprised only of that element, it is a pure substance. A chunk of copper, oxygen gas, a lead weight, and a diamond (pure carbon) are prime examples of a pure substance that is in an elemental form.
lead (Pb), a soft, silvery white or grayish metal in Group 14 (IVa) of the periodic table. Lead is very malleable, ductile, and dense and is a poor conductor of electricity. Known in antiquity and believed by the alchemists to be the oldest of metals, lead is highly durable and resistant to corrosion, as is indicated by the continuing use of lead water pipes installed by the ancient Romans. The symbol Pb for lead is an abbreviation of the Latin word for lead, plumbum.
Lead is a naturally occurring bluish-gray metal found in small amounts in the earth’s crust. Also Lead can be found in all parts of our environment. Much of it comes from human activities including burning fossil fuels, mining, and manufacturing.Lead has many different uses. It is used in the production of batteries, ammunition, metal products (solder and pipes), and devices to shield X-rays. Because of health concerns, lead from gasoline, paints and ceramic products, caulking, and pipe solder has been dramatically reduced in recent years.
*CDC has updated its recommendations on children’s blood lead levels. Experts now use an upper reference level value of 97.5% of the population distribution for children’s blood lead. In 2012-2015 that value is 5 micrograms per deciliter (µg/dL) to identify children with blood lead levels that are much higher than most children’s levels. The information on this page refers to CDC’s previous “blood lead level of concern” of 10 µg/dL. This information will be updated in future ToxProfile and ToxFAQ editions. To learn more about CDC’s updated recommendations on children’s blood lead levels.
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Lead Occurrence and distribution
Lead is mentioned often in early biblical accounts. The Babylonians used the metal as plates on which to record inscriptions. The Romans used it for tablets, water pipes, coins, and even cooking utensils; indeed, as a result of the last use, lead poisoning was recognized in the time of Augustus Caesar. The compound known as white lead was apparently prepared as a decorative pigment at least as early as 200 BCE. Modern developments date to the exploitation in the late 1700s of deposits in the Missouri-Kansas-Oklahoma area in the United States.
Pure Substances
When we speak of a pure substance, we are speaking of something that contains only one kind of matter. This can either be one single element or one single compound, but every sample of this substance that you examine must contain exactly the same thing with a fixed, definite set of properties.
| Pure Substance | Element or Compound? | Consists of: |
|---|---|---|
| Lead (Pb) | element | lead atoms |
| Oxygen gas (O2) | element | oxygen molecules* |
| Water (H2O) | compound | water molecules |
| Ammonia (NH3) | compound | ammonia molecules |
*Note: pure oxygen gas consists of molecules but it is still considered an element, rather than a compound, as the molecules are made up of a single type of element. Compounds are made up of one or more element.
Mixtures
If we take two or more pure substances and mix them together, we refer to this as a mixture. Mixtures can always be separated again into component pure substances, because bonding among the atoms of the constituent substances does not occur in a mixture. Whereas a compound may have very different properties from the elements that compose it, in mixtures the substances keep their individual properties. For example sodium is a soft shiny metal and chlorine is a pungent green gas.
These two elements can combine to form the compound, sodium chloride (table salt) which is a white, crystalline solid having none of the properties of either sodium or chlorine. If, however, you mixed table salt with ground pepper, you would still be able to see the individual grains of each of them and, if you were patient, you could take tweezers and carefully separate them back into pure salt and pure pepper.
Heterogeneous mixture
A heterogeneous mixture is a mixture in which the composition is not uniform throughout the mixture. Vegetable soup is a heterogeneous mixture. Any given spoonful of soup will contain varying amounts of the different vegetables and other components of the soup.
Homogeneous mixture/ Solution
A homogeneous mixture is combination of two or more substances that are so intimately mixed that the mixture behaves as a single substance. Another word for a homogeneous mixture is solution. Thus, a combination of salt and steel wool is a heterogeneous mixture because it is easy to see which particles of the matter are salt crystals and which are steel wool. On the other hand, if you take salt crystals and dissolve them in water, it is very difficult to tell that you have more than one substance present just by looking—even if you use a powerful microscope. The salt dissolved in water is a homogeneous mixture, or a solution.
| Group | 14 | Melting point | 327.462°C, 621.432°F, 600.612 K |
| Period | 6 | Boiling point | 1749°C, 3180°F, 2022 K |
| Block | p | Density (g cm−3) | 11.3 |
| Atomic number | 82 | Relative atomic mass | 207.2 |
| State at 20°C | Solid | Key isotopes | 208Pb |
| Electron configuration | [Xe] 4f145d106s26p2 | CAS number | 7439-92-1 |
On a weight basis, lead has nearly the same abundance in Earth’s crust as tin. Cosmically, there is 0.47 lead atom per 106 silicon atoms. The cosmic abundance is comparable to those of cesium, praseodymium, hafnium, and tungsten, each of which is regarded as a reasonably scarce element.
Although lead is not abundant, natural concentration processes have resulted in substantial deposits of commercial significance, particularly in the United States but also in Canada, Australia, Spain, Germany, Africa, and South America. Significant deposits are found in the United States in the western states and the Mississippi valley. Rarely found free in nature, lead is present in several minerals, but all are of minor significance except the sulfide, PbS (galena, or lead glance), which is the major source of lead production throughout the world. Lead is also found in anglesite (PbSO4) and cerussite (PbCO3). By the early 21st century, China, Australia, the United States, Peru, Mexico, and India were the world’s top producers of lead in concentrate.
