Actinium

-
.
Actinium, symbol Ac, radioactive metallic element found in all uranium ores. The atomic number of actinium is 89; the element is in the actinide series of the periodic table.

Actinium was discovered in 1899 by the French chemist André Louis Debierne. The element is found in uranium ores to the extent of 2 parts to every 10 billion parts of uranium. Two naturally occurring isotopes of actinium are known. Actinium-227 is a member of the actinium series, called the actinium decay series, resulting from the radioactive decay of uranium-235 (see Radioactivity). It has a half-life of 21.8 years. The other isotope, actinium-228, is a member of the thorium series resulting from the decay of thorium-232. This isotope, known also as mesothorium-2, has a half-life of 6.13 hours. Isotopes ranging in mass number from 209 to 234 are known. Actinium melts at about 1050° C (about 1922° F), boils at about 3200° C (about 5792° F), and has a specific gravity of about 10.

Comments

Post a Comment

Popular posts from this blog

Converting Food to Usable Energy

-
Cellular respiration is a complex series of chemical reactions that harvests the energy trapped in the bonds of glucose sugar molecules and converts it into a chemical form that can be stored for later use. Humans and other animals obtain glucose sugar molecules from food, such as the fruits and grains shown here, while plants create glucose sugars in the process of photosynthesis. Essential to the survival of most organisms on Earth, cellular respiration yields the energy that makes our bodies function properly.
Read more

Electrical Conductor

-
. Electrical Conductor, any material that offers little resistance to the flow of an electric current. The difference between a conductor and an insulator, which is a poor conductor of electricity or heat , is one of degree rather than kind, because all substances conduct electricity to some extent. A good conductor of electricity, such as silver or copper , may have a conductivity a billion or more times as great as the conductivity of a good insulator, such as glass or mica. A phenomenon known as superconductivity is observed when certain substances are cooled to a point near absolute zero , at which point their conductivity becomes almost infinite. In solid conductors the electric current is carried by the movement of electrons; in solutions and gases , the electric current is carried by ions.
Read more

Starch

-
Starch , common name applied to a white, granular or powdery, odorless, tasteless, complex carbohydrate, (C 6 H 10 O 5 ) x , abundant in the seeds of cereal plants and in bulbs and tubers. Molecules of starch are made of hundreds or thousands of atoms, corresponding to values of x, as given in the formula above, that range from about 50 to many thousands. Starch molecules are of two kinds. In the first kind, amylose, which constitutes about 20 percent of ordinary starch, the C 6 H 10 O 5 groups are arranged in a continuous but curled chain somewhat like a coil of rope; in the second kind, amylopectin, considerable side-branching of the molecule occurs. Starch is manufactured by green plants during the process of photosynthesis . It forms part of the cell walls in plants, constitutes part of rigid plant fibers, and serves as a kind of energy storage for plants, because its oxidation to carbon dioxide and water releases energy. The granules of starch present in any...
Read more