CHEMISTRY 2


Strontium.

The flame test for strontium is a brilliant dark red. This color is spectacularly shown in fireworks displays with strontium salts. Elemental strontium is a hard silvery metal of Group 2, very similar to calcium. Strontium 90, a radioactive isotope of strontium, can be in the fallout from nuclear explosions. It has been recorded that strontium 90 landing on vegetation eaten by dairy cattle can appear in the milk of those animals, similarly the usual calcium.


Sulfur.

The brimstone of the Bible, sulfur was most likely encountered by prehistoric humankind near geothermal sources such as volcanoes and geysers. Sulfur's two crystal forms, monoclinic and rhombic, both have a melting temperature just above the boiling point of water at one atmosphere. Under pressure, as under the earth, water temperature can exceed the melting temperature for sulfur. Since sulfur does not dissolve in water, the liquid sulfur immediately solidifies as it reaches the earth's surface, leaving the distinctive non-metal pale yellow brittle solid. The Frasch process for mining sulfur does exactly the same as the geothermal process.

Superheated water under pressure is pumped into the earth and retrieved with melted sulfur in it, mimicking the natural process for sulfur exposure. There is another non-crystalline form of elemental sulfur that can be made by melting crystalline sulfur, but the amorphous allotrope is unstable, reverting to one of the crystalline forms on standing. Sulfur burns in air (the stone that burns) to form sulfur dioxide. This is the first step in the manufacture of sulfuric acid, by far the most used compound of sulfur. It has been said that the amount of sulfuric acid made is a good measure of the level of industrialization of a country. Sulfur is one of the main ingredients in the vulcanization of rubber.


Tin.

Tin was the secret ingredient in bronze that made it possible for the copper alloy to hold a minimal edge for swords. Tin is a metal element that has a characteristic tendency to form crystals in the solid metal. It does not react with mild acids or the normal constituents of the air, making it usable as a coating to cheaper metals. Iron or steel coated with tin or zinc, called Galvanized, is used for 'tin roofing,' 'tin cans,' and 'tin soldiers' (perhaps even 'tin woodmen'). It is easy to spot when tin is used to cover other metals because of the large crystals appearing on the surface. Pewter and solder are other important alloys of tin.


Titanium.

The ores of titanium are not very common, but the metal is a very light, strong metal. Titanium is much stronger per mass than iron. Airplanes, bicycles, and ultracentrifuge rotors are some of the items that work best made of titanium because of its lightness (small density) and great tensile strength. Titanium oxide makes a beautiful white pigment.


Tritium. Tritium is the heaviest known isotope of hydrogen, having one proton and two neutrons. It is not an element. See 'deuterium'.


Tungsten.

Having a melting point of almost six thousand degrees Celsius and good electrical conductivity, Tungsten makes a good light bulb filament. It is a hard, brittle metal. The great majority of tungsten is used to alloy with steel to make a hard, tough metal for uses like high speed drilling and cutting tools.


Uranium.

The highest atomic number of the naturally occurring elements, uranium has a fissionable isotope. Some of the first �atomic bombs� were fission devices with uranium. Some nuclear energy facilities use uranium as the fuel to make electricity. Some of the yellow or black compounds of uranium were used in ceramic glazes.


Xenon.

The heaviest and the rarest of the naturally occurring inert gases in air, xenon produces a beautiful blue glow in fluorescent tubes. It has the highest boiling point of the natural inert gases at -107 �C. As the other inert gases, it makes no natural compounds.


Zinc.

For many centuries zinc was included in the metals of brass without being recognized as an element. The element zinc is used to cover other metals to protect from oxidation and as one electrode in some electric cells. Elemental zinc is a bluish metal that has the surprising property of being slightly brittle at room temperature, but more malleable at or above 100 �C. Zinc metal is used to alloy with other metals. Zinc oxide is used as an antiseptic and as a white pigment.

- Chem Tutor




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