Chapter 1 Introduction to Chemistry1.6 Isotopes and Atomic Masses84
1.7 Introduction to the Periodic TableLEARNING OBJECTIVE1.To become familiar with the organization of the periodic table.The elements are arranged in aperiodic table(Figure 1.24 "The Periodic TableShowing the Elements in Order of Increasing "; also seeChapter 32 "Appendix H:Periodic Table of Elements"), which is probably the single most important learningaid in chemistry. It summarizes huge amounts of information about the elements ina way that permits you to predict many of their properties and chemical reactions.The elements are arranged in seven horizontal rows, in order of increasing atomicnumber from left to right and top to bottom. The rows are calledperiods46, andthey are numbered from 1 to 7. The elements are stacked in such a way thatelements with similar chemical properties form vertical columns, calledgroups47,numbered from 1 to 18 (older periodic tables use a system based on romannumerals). Groups 1, 2, and 13–18 are themain group elements48, listed asAinolder tables. Groups 3–12 are in the middle of the periodic table and are thetransition elements49, listed asBin older tables. The two rows of 14 elements atthe bottom of the periodic table are thelanthanidesand theactinides, whosepositions in the periodic table are indicated in group 3. A more comprehensivedescription of the periodic table is found inChapter 7 "The Periodic Table andPeriodic Trends".Metals, Nonmetals, and SemimetalsThe heavy orange zigzag line running diagonally from the upper left to the lowerright through groups 13–16 inFigure 1.24 "The Periodic Table Showing theElements in Order of Increasing "divides the elements intometals50(in blue, belowand to the left of the line) andnonmetals51(in bronze, above and to the right of theline). As you might expect, elements colored in gold that lie along the diagonal lineexhibit properties intermediate between metals and nonmetals; they are calledsemimetals52.The distinction between metals and nonmetals is one of the most fundamental inchemistry. Metals—such as copper or gold—are good conductors of electricity andheat; they can be pulled into wires because they areductile53; they can behammered or pressed into thin sheets or foils because they aremalleable54; andmost have a shiny appearance, so they arelustrous55. The vast majority of the46. A row of elements in theperiodic table.47. A vertical column of elementsin the periodic table. Elementswith similar chemicalproperties reside in the samegroup.48. Any element in groups 1, 2, and13–18 in the periodic table.These groups contain metals,semimetals, and nonmetals.49. Any element in groups 3–12 inthe periodic table. All of thetransition elements are metals.
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