CHAPTER OUTLINE Section 1 Organizing the Elements Key Idea questions > How did Mendeleev arrange the elements in his periodic table? > How are elements arranged in the modern periodic table? Recognizing a Pattern > How did Mendeleev arrange the elements in his periodic table? > In his periodic table, Mendeleev arranged elements in rows by increasing atomic mass. Mendeleev was able to predict new elements. Mendeleev left spaces in his table to make the pattern fit. He used the spaces to successfully predict the existence and properties of elements not yet discovered. A few elements did not fit the pattern. Changing the Arrangement > How are elements arranged in the modern periodic table? > The modern periodic table organizes elements by atomic number. When the elements are arranged in this way, elements that have similar properties appear at regular intervals. As scientists learned more about the structure of the atom, they improved Mendeleev s table. Arranging the table by atomic number (number of protons) rather than by atomic mass fixed the discrepancies in Mendeleev s table. periodic law: the law that states that the repeating chemical and physical properties of elements change periodically with the atomic numbers of the elements Super Summary Chapter Outline p. 1
Elements become less metallic across each period. period: a horizontal row of elements in the periodic table Elements in a group have similar properties. group: a vertical column of elements in the periodic table; elements in a group share chemical properties Super Summary Chapter Outline p. 2
Section 2 Exploring the Periodic Table Key Idea questions > Why do elements within a group of the periodic table have similar chemical properties? > What happens to an atom that gains or loses electrons? > What are the three main categories of elements? The Role of Electrons > Why do elements within a group of the periodic table have similar chemical properties? > The periodic trends in the periodic table are the result of electron arrangement. Valence electrons account for similar properties. An element s location in the periodic table is related to electron arrangement. Example: Lithium and sodium, in Group 1, each have one valence electron. Ion Formation > What happens to an atom that gains or loses electrons? > If an atom gains or loses electrons, it no longer has an equal number of electrons and protons. Because the charges do not cancel completely, the atom has a net electric charge. Group 1 elements form positive ions. The single valence electron is easily removed. Group 17 elements form negative ions. The addition of one valence electron fills the outer energy level. Super Summary Chapter Outline p. 3
How Are Elements Classified? > What are the three main categories of elements? > All elements are either metals, nonmetals, or semiconductors. Elements in each category have similar properties. metal: an element that is shiny and that conducts heat and electricity well nonmetal: an element conducts heat and electricity poorly semiconductor (or metalloid): an element or compound that conducts electric current better than an insulator does but not as well as a conductor does Super Summary Chapter Outline p. 4
Section 3 Families of Elements Key Idea questions > What does each element family have in common? > What are the families of metals? > What are some of the families of nonmetals? > What are semiconductors? Classifying Elements Further > What does each element family have in common? > In general, the elements in a family have the same number of valence electrons. Metals > What are the families of metals? > Families of metals include the alkali metals, the alkaline-earth metals, and the transition metals. alkali metal: one of the elements of Group 1 of the periodic table alkaline-earth metal: one of the elements of Group 2 of the periodic table transition metal: one of the metals that can use the inner shell before using the outer shell to bond The alkali metals are very reactive. Alkaline-earth metals form compounds that are found in limestone and in the human body. Transition metals are in the middle of the periodic table. Super Summary Chapter Outline p. 5
Nonmetals > What are some of the families of nonmetals? > Families of nonmetals include the noble gases and the halogens. noble gas: one of the elements of Group 18 of the periodic table halogen: one of the elements of Group 17 of the periodic table The noble gases are relatively inert. The halogens combine easily with metals to form salts. Nonmetals and their compounds are plentiful on Earth. Semiconductors > What are semiconductors? > As their name suggests, semiconductors are able to conduct heat and electricity under certain conditions. Super Summary Chapter Outline p. 6