CH-01Rev. 0Page 12THE PERIODIC TABLEDOE-HDBK-1015/1-93Fundamentals of ChemistryTHE PERIODIC TABLEAll known elements fall into a pattern when placed in a periodic table, andthe position in this pattern is decided by the element's atomic number. Thischapter will discuss the significance of this fact.EO 1.4DEFINE the following subdivisions of the periodic table:a.Periods of the periodic tableb.Groups of the periodic tablec.Classes of the periodic tableEO 1.5Given a periodic table, IDENTIFY thefollowing subdivisions:a.Periods of the periodic tableb.Groups of the periodic tablec.Classes of the periodic tableEO 1.6LIST the characteristics that elements in thesame group on the periodic table share.EO 1.7DEFINE the term valence.PeriodicTableOver many years of chemical investigation, scientists have discovered a remarkable featureof the elements. If the elements are arranged in the order of their atomic numbers, thechemical properties of the elements are repeated somewhat regularly. To a lesser extent, thephysical properties are also repeated periodically. This periodic repetition can be seen inTable 3. Compare the properties of lithium (Li), sodium (Na), and potassium (K), and alsothose of beryllium (Be), magnesium (Mg), and calcium (Ca). In the list of elements shownin Table 3 the properties are repeated every eighth element.TABLE 3Description of the Properties of the First Twenty ElementsElementSymbolAtomicAtomicDescription of PropertiesNumberWeightHydrogenH11.008Colorless gas, reacts readily with oxygen to form H O; 2forms HCl with chlorine.HeliumHe24.003Colorless gas, very non-reactive chemically.
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