The following sections of this BookRags Literature Study Guide is offprint from Gale's For Students Series: Presenting Analysis, Context, and Criticism on Commonly Studied Works: Introduction, Author Biography, Plot Summary, Characters, Themes, Style, Historical Context, Critical Overview, Criticism and Critical Essays, Media Adaptations, Topics for Further Study, Compare & Contrast, What Do I Read Next?, For Further Study, and Sources.
(c)1998-2002; (c)2002 by Gale. Gale is an imprint of The Gale Group, Inc., a division of Thomson Learning, Inc. Gale and Design and Thomson Learning are trademarks used herein under license.
The following sections, if they exist, are offprint from Beacham's Encyclopedia of Popular Fiction: "Social Concerns", "Thematic Overview", "Techniques", "Literary Precedents", "Key Questions", "Related Titles", "Adaptations", "Related Web Sites". (c)1994-2005, by Walton Beacham.
The following sections, if they exist, are offprint from Beacham's Guide to Literature for Young Adults: "About the Author", "Overview", "Setting", "Literary Qualities", "Social Sensitivity", "Topics for Discussion", "Ideas for Reports and Papers". (c)1994-2005, by Walton Beacham.
All other sections in this Literature Study Guide are owned and copyrighted by BookRags, Inc.
The radius of an atom is defined as half the distance between the nuclei of two atoms in a pure sample of the substance. The measurements have been obtained through x- ray diffraction techniques. The periodic table displays two significant relationships about the radii of atoms: 1) as elements increase in atomic number in a period, going from Group IA to Group 7A, the atomic radius decreases; 2) as elements in the same group increase in atomic number, the atomic radius increases. The largest atom has a radius that is only twice the size of the smallest.
The reason that the radii of the atoms within a period decreases relates to the electric force between the positively charged nucleus and the negatively charged electrons orbiting it. The number of protons in the nucleus is increased from Group IA to Group 7A. Adding protons to the nucleus results in a greater electric force. When the force of attraction increases, the electrons are drawn closer to the nucleus.
The reason that the radius of the atom increases within a group as the period number increases is the location of outer electrons in higher energy levels. These electrons have a higher probability of being located farther from the nucleus, resulting in a larger atomic radius. There is also a shielding effect by the core electrons, decreasing the force of attraction between the nucleus and the valence electrons.