Architecture tradeoff analysis method: Difference between revisions

Revision as of 19:36, 4 February 2008

Revision as of 19:36, 4 February 2008

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POTASSIUM

Potassium is a chemical element. It has the symbol K and atomic number19. The name "potassium" comes from the word "potash", as potassium was first isolated from potash. Potassium is a soft silvery-white metallic alkali metal that occurs naturally bound to other elements in seawater and many minerals. It oxidizes rapidly in air and is very reactive, especially towards water. In many respects, potassium and sodium are chemically similar, although organisms in general, and animal cells in particular, treat them very differently.

Potassium makes up about 1.5% of the weight of the Earth's crust and is the seventh most abundant element. As it is very electropositive, potassium metal is difficult to obtain from its minerals. It is never found free in nature, as it reacts violently with water. Potassium salts such as carnallite, langbeinite, polyhalite, and sylvite are found in ancient lake and sea beds. These minerals form extensive deposits in these environments, making extracting potassium and its salts more economical. The principal source of potassium, potash, is mined in Saskatchewan, California, Germany, New Mexico, Utah, and in other places around the world. Three thousand feet below the surface of Saskatchewan are large deposits of potash which are important sources of this element and its salts, with several large mines in operation since the 1960s. Saskatchewan pioneered the use of freezing of wet sands (the Blairmore formation) in order to drive mine shafts through them. The main mining company is the Potash Corporation of Saskatchewan. The oceans are another source of potassium, but the quantity present in a given volume of seawater is relatively low compared with sodium.

Potassium can be isolated through electrolysis of its hydroxide in a process that has changed little since Davy. Thermal methods also are employed in potassium production, using potassium chloride.

See also potassium minerals.

NUCLEUS

The nucleus of an atom is the very small dense region of an atom, in its center consisting of nucleons (protons and neutrons). The size (diameter) of the nucleus is in the range of 1.6 fm (10-15 m) (for a proton in light hydrogen) to about 15 fm (for the heaviest atoms, such as uranium). These dimensions are much smaller than the size of the atom itself by a factor of about 23,000 (uranium) to about 145,000 (hydrogen). Almost all of the mass in an atom is made up from the protons and neutrons in the nucleus with a very small contribution from the orbiting electrons. The etymology of the term nucleus is from 1704 meaning “kernel of a nut”. In 1844, Michael Faraday used the term to refer to the “central point of an atom”. The modern atomic meaning was proposed by Ernest Rutherford in 1912.[1] The adoption of the term “nucleus” to atomic theory, however, was not immediate. In 1916, for example, Gilbert N. Lewis stated, in his famous article The Atom and the Molecule, that “the atom is composed of the kernel and an outer atom or shell”.

PROTONS

In physics, the proton (Greek πρώτον / proton = first) is a subatomic particle with an electric charge of one positive fundamental unit (1.602 × 10−19 coulomb), a diameter of about 1.6 to 1.7×10−15 m [1], and a mass of 938.27231(28) MeV/c2 (1.6726 × 10−27 kg), 1.007 276 466 88(13) u or about 1836 times the mass of an electron.

Protons are spin-1/2 fermions and are composed of three quarks[2], making them baryons. The two up quarks and one down quark of the proton are also held together by the strong nuclear force, mediated by gluons.

Protons and neutrons are both nucleons, which may be bound by the nuclear force into atomic nuclei. The most common isotope of the hydrogen atom is a single proton (it contains no neutrons). The nuclei of other atoms are composed of various numbers of protons and neutrons. The number of protons in the nucleus determines the chemical properties of the atom and which chemical element it is (the number of neutrons and protons contribute to the mass of that isotope; also the way in which the atoms are arranged in the lattice(mathematics) determines its physical properties, like binding energy etc; this is called the element's allotrope).

NEUTRONS

In physics, the neutron is a subatomic particle with no net electric charge and a mass of 939.573 MeV/c² or 1.008 664 915 (78) u (1.6749 × 10−27 kg, slightly more than a proton). Its spin is ½. Its antiparticle is called the antineutron. The neutron, along with the proton, is a nucleon.

The nuclei of all atoms consist of protons and neutrons, except the lightest isotope of hydrogen which has only a single proton. The number of protons defines the type of element the atom forms. The number of neutrons determines the isotope of an element, therefore isotopes are atoms of the same element (i.e. atomic number) but differing atomic masses due to a different number of neutrons. For example, the carbon-12 isotope has 6 protons and 6 neutrons, while the carbon-14 isotope has 6 protons and 8 neutrons.

A neutron consists of two down quarks and one up quark. Since it has three quarks, it is classified as a baryon.

ORBITS

In physics, an orbit is the path that an object makes around another object while under the influence of a central force, such as gravity.

POSITIVE