The Periodic Table

Chapter 5 The Periodic Table Table of Contents Section 1 Arranging the Elements Section 2 Grouping the Elements

Chapter 5 Section1 Arranging the Elements Objectives • Describe how Mendeleev arranged elements in the first periodic table. • Explain how elements are arranged in the modern periodic table. • Compare metals, nonmetals, and metalloids based on their properties and on their location in the periodic table. • Describe the difference between a period and a group.

Chapter 5 Section1 Arranging the Elements Discovering a Pattern • In 1869, Russian chemist Dmitri Mendeleev arranged the elements in order of increasing atomic mass. • Periodic Properties of the ElementsWhen the elements are arranged in order of increasing atomic mass, those that had similar properties occurred in a repeating pattern. • These repeating patterns areperiodic,meaning that they happen at regular intervals.

Chapter 5 Section1 Arranging the Elements Discovering a Pattern, continued • Predicting Properties of Missing ElementsMendeleev’s arrangement had gaps in its pattern. Mendeleev predicted that elements yet to be found would fill these gaps. He also predicted the properties of the missing elements. • By 1886, all of the gaps had been filled and Mendeleev’s predictions were right.

Chapter 5 Section1 Arranging the Elements Changing the Arrangement • A few elements’ properties did not fit in the pattern of Mendeleev’s table. • In 1914, British scientist Henry Moseley found the number of protons—the atomic number—in an atom. • When the elements were arranged by atomic number, they fit the pattern in Mendeleev’s table.

Chapter 5 Section1 Arranging the Elements

Chapter 5 Section1 Arranging the Elements The Periodic Table and Classes of Elements • Elements are classified as metals, nonmetals, and metalloids, according to their properties. • The number of electrons in the outer energy level of an atom is one characteristic that helps determine which category an element belongs in. • The zigzag line on the periodic table can help you recognize which elements belong in which category.

Chapter 5 Section1 Arranging the Elements The Periodic Table and Classes of Elements, continued • Metalsare found to the left of the zigzag line. Atoms of most metals have few electrons in their outer energy level. • Most metals are shiny, ductile, malleable, and are good conductors of electric current and thermal energy.

Chapter 5 Section1 Arranging the Elements The Periodic Table and Classes of Elements, continued • Nonmetalsare found to the right of the zigzag line. Atoms of most nonmetals have an almost complete set of electrons in their outer energy level. • Nonmetals are not shiny, ductile, or malleable, and are poor conductors of electric current and thermal energy.

Chapter 5 Section1 Arranging the Elements The Periodic Table and Classes of Elements, continued • Metalloidsare the elements that border the zigzag line. Atoms of metalloids have about half of a complete set of electrons in their outer energy level. • Metalloids have some properties of metals and some properties of nonmetals. • Metalloids are also called semiconductors.

Chapter 5 Section1 Arranging the Elements Decoding the Periodic Table • Each Element is Identified by a Chemical SymbolEach square on the periodic table includes an element’s name, chemical symbol, atomic number, and atomic mass. • For most elements, the chemical symbol has one or two letters. The newest elements have temporary three-letter symbols.

Chapter 5 Section1 Arranging the Elements Decoding the Periodic Table, continued • Rows Are Called PeriodsEach horizontal row of elements is called aperiod.The chemical and physical properties of elements in a row follow a repeating pattern as you move across the period. • Columns Are Called GroupsEach vertical column of elements is called agroup.Elements in the same group often have similar chemical and physical properties.

Chapter 5 Section1 Arranging the Elements Periodic Table Overview

Chapter 5 Section2 Grouping the Elements Bellringer Think about the following: How do you know that a bird is a bird? A kangaroo is a kangaroo? A shark is a shark? What characteristics of each animal help you to tell them apart? How does this apply to elements? Record your answers in yourscience journal.

Chapter 5 Section2 Grouping the Elements Objectives • Explain why elements in a group often have similar properties. • Describe the properties of the elements in the groups of the periodic table.

Chapter 5 Section2 Grouping the Elements Group 1: Alkali Metals • Alkali metals are elements in Group 1 of the periodic table. Alkali metal properties: • group contains metals • 1 electron in the outer level • very reactive • softness, color of silver, shininess, low density

Chapter 5 Section2 Grouping the Elements Group 2: Alkaline-Earth Metals • Alkaline-earth metals are elements in Group 2. Alkaline-earth metal properties: • group contains metals • 2 electrons in the outer level • very reactive, but less reactive than alkali metals • color of silver, higher densities than alkali metals

Chapter 5 Section2 Grouping the Elements Group 3–12: Transition Metals • Transition metals are inGroups 3–12. Some of the transition metals are shown below.

Chapter 5 Section2 Grouping the Elements Group 3–12: Transition Metals, continued • Properties of Transition Metalsvary widely but include: • groups contains metals • 1 or 2 electrons in the outer level • less reactive than alkaline-earth metals • shininess, good conductors of electric current and thermal energy

Chapter 5 Section2 Grouping the Elements Group 3–12: Transition Metals, continued • Lanthanides and Actinides Some transition metals from Periods 6 and 7 appear in two rows at the bottom of the periodic table. Elements in the first row are called lanthanides and elements in the second row are called actinides.

Chapter 5 Section2 Grouping the Elements Group 13: Boron Group • Aluminum is the most common element from Group 13. Group 13 properties: • group contains one metalloid and four metals • 3 electrons in the outer level • reactive • solids at room temperature

Chapter 5 Section2 Grouping the Elements Group 14: Carbon Group • Group 14 properties: • group contains one nonmetal, two metalloids, and two metals • 4 electrons in the outer level • reactivity varies among the elements • solids at room temperature

Chapter 5 Section2 Grouping the Elements Group 15: Nitrogen Group • Group 15 properties: • group contains two nonmetals, two metalloids, and one metal • 5 electrons in the outer level • reactivity varies among the elements • solids at room temperature (except for nitrogen, which is a gas)

Chapter 5 Section2 Grouping the Elements Group 16: Oxygen Group • Group 16 properties: • group contains three nonmetals, one metalloids, and one metal • 6 electrons in the outer level • reactive • solids at room temperature (except for oxygen, which is a gas)

Chapter 5 Section2 Grouping the Elements Group 17: Halogens • Halogensare the elements in Group 17. Group 17 properties: • group contains nonmetals • 7 electrons in the outer level • very reactive • poor conductors of electric current, never in uncombined form in nature

Chapter 5 Section2 Grouping the Elements Group 18: Noble Gases • Noble gasesare the elements in Group 18. Group 18 properties: • group contains nonmetals • 8 electrons in the outer level (except helium, which has 2) • unreactive • colorless, odorless gases at room temperature

Chapter 5 Section2 Grouping the Elements Hydrogen • The properties of hydrogen do not match the properties of any single group, so hydrogen is set apart. • a nonmetal • 1 electron in the outer level • reactive • colorless, odorless gas at room temperature, low density

Chapter 5 The Periodic Table Concept Mapping Use the terms below to complete the concept map on the next slide.

Chapter 5 The Periodic Table

End of Chapter 5 Show Chapter menu Resources

Chapter 5 Standardized Test Preparation The graph below shows the densities in kilograms per cubic meter (kg/m3) of the elements in Period 2 of the periodic table. The densities of the elements of Period 3 follow this trend.

Chapter 5 Standardized Test Preparation 1. Which of the following elements is most likely to have a lower density than calcium (Ca) has? A. gallium (Ga) B. germanium (Ge) C. potassium (K) D. selenium (Se)

Chapter 5 Standardized Test Preparation 2. In Mendeleev’s periodic table, the element iodine (I) came before tellurium (Te). He arranged the elements by atomic weight. Later, Henry Moseley revised the table to place iodine after tellurium. Moseley’s version of the periodic table is still in use today. Explain the basis for Moseley’s revision to the periodic table.

Chapter 5 Standardized Test Preparation • 2. Explain the basis for Moseley’s revision to the periodic table. • Full-credit answers should include the following points: • Moseley’s version of the periodic table is based on atomic number. • Some elements have higher atomic weights than neighboring elements that have higher atomic numbers. • Therefore, some elements were rearranged when atomic numbers were discovered and used to organize the periodic table.

Chapter 5 Standardized Test Preparation The diagram below is an enlargement of a section of the periodic table.

Chapter 5 Standardized Test Preparation 3. What is the biggest difference between cobalt (Co) and nickel (Ni) as shown in the periodic table entries? F. Nickel has more protons. G. Cobalt has more electrons. H. Cobalt has a lower number of neutrons. I. Nickel has a higher value for atomic mass.

Chapter 5 Standardized Test Preparation The table below shows some properties of copper and tungsten. In the table, the density of the elements are given in grams per cubic centimeter (g/cm3). When making coins, a large machine squashes the metal into the coin shape.

Chapter 5 Standardized Test Preparation 4. Which property of copper makes copper easier to form into coins than tungsten? A. lower density B. lower hardness C. higher reflectivity D. higher heat conductivity

Chapter 5 Section2 Grouping the Elements

The Periodic Table