Jennifer Kim
Professor Cook
26 September 2005

Pre-Lab Study Questions:

1. Where are the valence electrons in an atom? Valence electrons are represented as dots around the symbol of an atom. (outermost shall or the valence shell)

2. How are positive and negative ions formed? The loss of one or more electrons from a neutral atom gives a positive charge (cation) and the gain of one or more electrons by a neutral atom gives a negative charge (anion).

3. How do subscripts represent the charge balance of ions? When two or more polyatomic ions are needed, the forumla of the ion is enclosed in parentheses and the subscript is place outside. No change is ever made in the forumla of the polyatomic ion itself.

4. Why are electrons shared in covalent compounds? Octets are achieved by sharing electrons between atoms.

5. How do the names of covalent compounds differ from the names of ionic compounds? In ionic compounds, the ions are named by replacing the ending of the nonmetal with ate or ite. For covalent compounds, the prefixes are derived from greek names: mono, di, tri, tetra, penta, hexa, hepta, octa. The second ends in ide.

6. What are polyatomic ions? A compound that consists of threeor more kinds of atoms.

7. How does the number of electron pairs around a central atom determine its shape? A molecule has a shape such as linear, bent, trigonal planar, pyramidal, or tetrahedral.The electron-pair repulsion (VSEPR) model indicates that the bond angles in a molecule are determined when the valence electrons in bonds and lone pairs move as far apart as possible. Counting the groups of electrons that are shared pairs and lone pairs determines the electron geometry and bond angle.

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