CHAPTER 5 Study Guide
5.1 Organizing the Elements
Key Concepts
Mendeleev arranged the elements into rows in order of increasing mass so that elements with similar properties were in the same column.
The close match between Mendeleev's predictions and the actual properties of new elements showed how useful his periodic table could be.
Vocabulary
periodic table, p. 127
5.2 The Modern Periodic Table
Key Concepts
In the modern periodic table, elements are arranged by increasing atomic number (number of protons). Each row on the table is a period. Each column is a group.
Properties of elements repeat in a predictable way when atomic numbers are used to arrange elements into groups.
Atomic mass is a value that depends on the distribution of an element's isotopes in nature and the masses of those isotopes.
Elements are classified as metals, nonmetals, and metalloids. Metals are elements that are good conductors of electric current and heat. Nonmetals are poor conductors of electric current and heat. Metalloids are elements with properties that fall between those of metals and nonmetals.
Across a period from left to right, the elements become less metallic and more nonmetallic in their properties.
Vocabulary
period, p. 131
group, p. 131
periodic law, p. 131
atomic mass unit (amu), p. 134
metals, p. 135
transition metals, p. 136
nonmetals, p. 136
metalloids, p. 136
5.3 Representative Groups
Key Concepts
Elements in a group have similar properties because they have the same number of valence electrons.
The alkali earth metals in Group 1A are extremely reactive. The reactivity of these metals increases from the top of the group to the bottom.
Differences in reactivity among the alkaline earth metals in Group 2A are shown by the ways they react with water.
Group 3A contains the most abundant metal in Earth's crust—aluminum. The energy needed to recycle aluminum is 5 percent of the energy needed to extract aluminum from bauxite.
Group 4A contains the nonmetal carbon. Most compounds in your body contain carbon. Carbon compounds control reactions that occur in cells.
Fertilizers usually contain the Group 5A elements nitrogen and phosphorus.
Oxygen, in Group 6A, is the most abundant element in Earth's crust.
Despite their physical differences, the halogens in Group 7A are all highly reactive nonmetals.
The noble gases, in Group 8A, are colorless and odorless and extremely unreactive.
Vocabulary
valence electron, p. 139
alkali metals, p. 140
alkaline earth metals, p. 141
halogens, p. 144
noble gases, p. 145
Thinking Visually
Web Diagram Use information from the chapter to complete the web diagram below. The web relates states of matter at room temperature to categories of elements.
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