Characteristics of Atoms Summary

Fundamentals of Chemistry DOE-HDBK-1015/1-93 CHARACTERISTICS OF ATOMS Rev. 0 CH-01 Page 11 Characteristics of Atoms Summary The following terms are defined: States of matter is a term which refers to the physical forms in which matter exists; solid, liquid and gas. Solids are characterized as having both a definite shape and a definite volume. Liquids have definite volumes but indefinite shapes and are slightly compressible. Gases are readily compressible and capable of infinite expansion. Atomic weight is defined as the weighted average of the masses of all its natural occurring isotopes. Molecular weight will be the total weight of the individual atoms of a molecule. A mole is Avogadro's number of any substance. Gram atomic weight is the mass of a mole of atoms. Gram molecular weight is the mass of a mole of molecules, (GMW). The components of an atom are protons, neutrons, and electrons. A proton has a mass of 1.0 amu and a positive charge (+1). The neutron also has a mass of 1.0 amu but is neutral in charge. The electron has a mass of .00055 or 1/1835 amu and a negative charge (-1). An atom is classified chemically by the number of protons in its nucleus. Summary The important information found in this chapter is summarized below.