WELCOME PARADISE VALLEY CC STUDENTS:
THIS IS YOUR "KNOW YOUR ELEMENTS" WEB SITE


HYDROGEN
(Greek for “water former”), symbol H, reactive, colorless, odorless, and tasteless gaseous element. The atomic number of hydrogen is 1. The element is usually classed in group 1 (or Ia) of the periodic table. Like most gaseous elements, hydrogen is diatomic (its molecules contain two atoms), but it dissociates into free atoms at high temperatures.


ELECTRON CONFIGURATION: 1s1

     Free hydrogen is found only in very small traces in the atmosphere, but solar and stellar spectra show that it is abundant in the sun and other stars, and is, in fact, the most common element in the universe. In combination with other elements it is widely distributed on the earth, where the most important and abundant compound of hydrogen is water, H2O. It is a component of all the constituents of living matter as well as of many minerals.
    It forms an essential part of all hydrocarbons and a vast variety of other organic substances. All acids contain hydrogen; the distinguishing characteristic of an acid is its dissociation, upon going in.to solution, to yield hydrogen ions.
    The lightest in weight of all gases, hydrogen has been used for the inflation of balloons and dirigibles. It ignites very easily, however, a small spark causing it to burn, and several dirigibles, including the Hindenburg, have been destroyed by hydrogen fires. Helium, which has 92 percent of the lifting power of hydrogen and is not inflammable, is used whenever possible.
    Hydrogen is known to exist in three isotopic forms. The nucleus of each atom of ordinary hydrogen is composed of one proton. Deuterium, present in ordinary hydrogen to the extent of 0.02 percent, contains one proton and one neutron in the nucleus of each atom and has an atomic mass of two. Tritium, an unstable, radioactive isotope, contains one proton and two neutrons in the nucleus of each atom, and has an atomic mass of three and constitutes only 1 in 1018 atoms of hydrogen.

HELIUM
(Greek helios, "sun"), symbol He, inert, colorless, odorless gaseous element. In group 18  of the periodic table.  Helium is one of the noble gases. The atomic number of helium is 2. The atomic weight of helium is 4.003.



ELECTRON CONFIGURATION:  1s2


The French astronomer Pierre Janssen discovered helium in the spectrum of the corona of the sun during an eclipse in 1868. Helium is the second most abundant element in the universe, after hydrogen.
    Helium has monatomic molecules, and is the lightest of all gases except hydrogen. . Helium, like the other noble gases, is chemically inert. Its single electron shell is filled, making possible reactions with other elements extremely difficult and the resulting compounds quite unstable. Helium is the most difficult of all gases to liquefy and is impossible to solidify at normal atmospheric pressures. These properties make liquid helium extremely useful as a refrigerant and for experimental work in producing and measuring temperatures close to absolute zero. Liquid helium can be cooled almost to absolute zero at normal pressure by rapid removal of the vapor above the liquid. At a temperature slightly above absolute zero, it is transformed into helium II, also called superfluid helium, a liquid with unique physical properties. It has no freezing point, and its viscosity is apparently zero; it passes readily through minute cracks and pores and will even creep up the sides and over the lip of a container. Helium-3, the lighter helium isotope of mass 3, which has an even lower boiling point than ordinary helium, exhibits markedly different properties when liquefied.
    Because it is noncombustible, helium is preferred to hydrogen as the lifting gas in lighter-than-air balloons; it has 92 percent of the lifting power of hydrogen, although it weighs twice as much. Helium is used to pressurize and stiffen the structure of rockets before takeoff and to pressurize the tanks of liquid hydrogen or other fuel in order to force fuel into the rocket engines. It is useful for this application because it remains a gas even at the low temperature of liquid hydrogen. A potential use of helium is as a heat-transfer medium in nuclear reactors because it remains chemically inert and nonradioactive under the conditions that exist within the reactors.
THINK ABOUT HELIUM'S CHEMICAL INERTNESS IN TERMS OF ITS HAVING ITS FIRST PRINCIPAL ENERGY LEVEL OR SHELL FILLED.  DOES THIS ELEMENT NEED TO TAKE OR DONATE ELECTRONS?

LITHIUM
Symbol Li, silvery white, chemically reactive metallic element that is the lightest in weight of all metals. In group 1 (or Ia) of the periodic table. Lithium is one of the alkali metals. The atomic number of lithium is 3.



ELECTRON CONFIGURATION: 1s2, 2s1


Chemically, lithium resembles sodium in its behavior in that both have an np1 valence electron. They form 1+ cations. It does not occur in nature in the free state but only in compounds, which are widely distributed.  Important compounds of lithium include the hydroxide, used for bonding carbon dioxide in the ventilator systems of spacecraft and submarines; and the hydride, used to inflate lifeboats.  Lithium carbonate, a common mineral, is used in the treatment of manic-depressive psychosis (principle component of psycho-active drugs such as Valium).

BERYLLIUM
Symbol Be, gray, brittle metallic element, with an atomic number of 4. It is in group 2 (or IIa) of the periodic table . Its atomic weight is 9.012.



ELECTRON CONFIGURATION: 1s2, 2s2


Beryllium, one of the alkaline earth metals.  It forms 2+ cations.
    The addition of beryllium to some alloys often results in products that have high heat resistance, improved corrosion resistance, greater hardness, greater insulating properties, and better casting qualities. Many parts of supersonic aircraft are made of beryllium alloys because of their lightness, stiffness, and dimensional stability.

CARBON



ELECTRON CONFIGURATION: 1s2, 2s2, 2p2


Symbol C, element that is crucial to the existence of living organisms, and that has many important industrial applications. The atomic number of carbon is 6; the element is in group 14  of the periodic table. Its atomic mass is 12.01115.

    The three forms of elemental carbon that occur in nature-diamond, graphite, and amorphous carbon-are solids with extremely high melting points and are insoluble in all solvents at ordinary temperatures. The physical properties of the three forms differ widely because of the differences in crystalline structure. In diamond, the hardest material known, each atom is linked to four other atoms in a three-dimensional framework, whereas graphite consists of weakly bonded plane layers of atoms that are arranged in hexagons.

    Carbon has the unique ability to link with other carbon atoms to form complex chains and rings. This property leads to an almost infinite number of carbon compounds, the most common being those containing carbon and hydrogen. The first carbon compounds were identified in living matter in the beginning of the 19th century, and therefore the study of carbon compounds was called "organic" chemistry.
    At normal temperatures carbon is characterized by a low reactivity. At high temperatures it reacts directly with most metals to form carbides, and with oxygen to form carbon monoxide (CO) and carbon dioxide (CO2). Carbon in the form of coke is used to remove oxygen from metal oxide ores in order to obtain the pure metal. Carbon also forms compounds with most of the nonmetallic elements.

    Carbon is a widely distributed element in nature; it occurs there mostly in the form of carbonates. Carbon dioxide is an important constituent of the atmosphere and is the main source of carbon incorporated in living matter. Plants, through the process of  photo-synthesis, convert carbon dioxide into organic carbon compounds, which are subsequently consumed by other organisms. THIS IS ONE OF THE MOST IMPORTANT BIOCHEMICAL REACTIONS THAT OCCURS ON EARTH.

The most common isotope of carbon is carbon-12; in 1961 this isotope was chosen to replace the isotope oxygen-16 as the standard for atomic weights, and was assigned the atomic weight of 12.

This web site was created from materials taken from Encarta Encyclopedia 96 from Microsoft.