Super Summary Chapter Outline p. 3. Section 2 Exploring the Periodic Table. Key Idea questions. > Why do elements within a group of the periodic table...
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
Chapter 5 The Periodic Table • 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
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.
Chapter 5 The Periodic Table 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
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.
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.
