The Elements of Earth's Crust
By Joan Whetzel
The Periodic Table lists 92 elements found naturally that make up the basic building blocks of life. Each element has its own composition, structure, and atomic weight. Eight of those elements make up approximately 99% of the Earth's crust. Listed by weight, they are: oxygen (46.3%), silicon (27.7%), aluminum (8.1%), iron (5.0%), calcium (3.6%), sodium (2.8%), potassium (2.6%), and magnesium (2.1%). Other elements found in the crust in trace amounts include: gold, silver, copper, and uranium.
The Periodic Table arranges the elements according to the chemical properties. Horizontal rows show the periods of each of the elements while vertical columns list the elements by groups based on their similar properties. .
Oxygen is a colorless, odorless, tasteless gas. In its liquid and solid sates, oxygen appears blue in color. An element in Group 16, oxygen makes up about 20% of the Earth's atmospheric gases and the 3rd most abundant element in the Sun. Compare that to Mars' atmosphere, which only has abouo0.15% oxygen. Two-thirds of the human body and 90% of all water consists of oxygen.
Silicon can be found in all stars including the Sun and is one of the main elements found in aerolite meteorites. Silica is found mainly in the form of silica oxides such as sand, quartz, rock crystals, amethyst, agate, flint, jasper and opals. Plant life needs the silica extracted from water as a component of their cell walls. It is also an important component of steel and carbide abrasives.
Aluminum, a silvery white metal, is light, nontoxic, nonmagnetic, and non-sparking. It is soft and malleable, making it easy to form, machine, and cast. As a soft metal, it is poor in strength by itself, but when combined with other metals (copper, magnesium, silicon, manganese) as an alloy, it becomes stronger and more useful for a number of uses. While it is quite abundant in the Earth's crust, it must be refined from bauxite (an aluminum ore) before it can be used.
Iron is fairly abundant in the universe, in the Sun and many other stars, in considerable quantities The atom nuclei for iron is quite stable. It is an important component of plant life and the hemoglobin in the blood of humans and animals. Iron is usually combined as an alloy with carbon to make steel. It corrodes easily when exposed to moist air and higher temperatures.
Calcium - a hard, alkaline, gray-silver metal - is an essential ingredient in leaves, bones, teeth, and shells. It does not occur by itself as a metal, but as part of various minerals such as limestone, gypsum, and fluorite. Even stalagmites and stalactites contain some calcium in the form of calcium carbonate (CaCO3), a mineral alloy that is the basis for concrete. Calcium reacts to air (leaving a white coating) and with water (burning with a yellow-red flame to form the nitride).
Sodium is an alkali metal, which gives an orange-yellow color to flames and turns street lights orange. Combined with chloride it forms common table salt which is important to human and animal nutrition.
Potassium, an alkali metal, is essential for plant growth and a vital element in our diet. Potassium can only be extracted by electrolysis of chloride or hydroxide. It is a soft, silvery metal that is easily cut with a knife. It decays in water, and burns in reaction to water, giving the flames a lilac purple color.
Magnesium - an alkaline, gray-white metal - is fairly strong. It will burn with a bright light. Magnesium is an essential element for plant life as well as for humans and animals.
Some of the important Periodic Table information for the elements in the Earth's crust are listed in the table below.
Windows to the Universe.Elements in the Earth's Crust.
Hyperphysics. Abundances of the Elements in the Earth's Crust.
Wikipedia. Abundance of Elements in the Earth's Crust.
Royal Society of Chemistry. Minerals, Elements and the Earth's Crust.
Israel Science and Technology. List of Periodic Table Elements Sorted by Abundance in Earth's Crust.
Web Elements. Periodic Table of the Elements.
Inside the Earth
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