chapter 12 section 1 arranging the elements...

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Section 1 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.

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Discovering a Pattern

•  In 1869, Russian chemist Dmitri Mendeleev arranged the elements in order of increasing atomic mass.

•  Periodic Properties of the Elements When the elements are arranged in order of increasing atomic mass, those that had similar properties occurred in a repeating pattern.

•  These repeating patterns are periodic, meaning that they happen at regular intervals.

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Discovering a Pattern, continued

•  Predicting Properties of Missing Elements Mendeleev�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.

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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.

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Section 1 Arranging the Elements Chapter 12




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.

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The Periodic Table and Classes of Elements, continued

•  Metals are 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.

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•  Nonmetals are 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.

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•  Metalloids are 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.

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Decoding the Periodic Table

•  Each Element is Identified by a Chemical Symbol Each 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.

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Decoding the Periodic Table, continued

•  Rows Are Called Periods Each horizontal row of elements is called a period. The chemical and physical properties of elements in a row follow a repeating pattern as you move across the period.

•  Columns Are Called Groups Each vertical column of elements is called a group. Elements in the same group often have similar chemical and physical properties.

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Section 2 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.

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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

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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

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Group 3–12: Transition Metals

•  Transition metals are in Groups 3–12. Some of the transition metals are shown below.

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Group 3–12: Transition Metals, continued

Properties of Transition Metals vary 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

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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.

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Group 13: Boron Group

Aluminum is the most common element from Group 13. Group 13 properties:

•  group contains one metalloid and five metals •  3 electrons in the outer level •  reactive •  solids at room temperature

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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

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Group 15: Nitrogen Group


•  group contains two nonmetals, two metalloids, and two metals •  5 electrons in the outer level •  reactivity varies among the elements •  solids at room temperature (except for nitrogen, which is a gas)

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Group 16: Oxygen Group


•  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)

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Group 17: Halogens

Halogens are 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

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Group 18: Noble Gases

Noble gases are 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

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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

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The Periodic Tables

Use the terms below to complete the concept map on the next slide.

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Concept Map

elements periods metals electrons

nonmetals periodic table groups (families)



The Periodic Table Chapter 12



Reading

Read each of the passages. Then, answer the questions that follow each passage.

Chapter 12 Standardized Test Preparation



Passage 1 Napoleon III (1808–1873) ruled as emperor of France from 1852 to 1870. Napoleon III was the nephew of the famous French military leader and emperor Napoleon I. Early in his reign, Napoleon III was an authoritarian ruler. France�s economy did well under his dictatorial rule, so the French rebuilt cities and built railways. Continued on the next slide




Passage 1, continued During the 1850s and 1860s, Napoleon III used aluminum dinnerware because aluminum was more valuable than gold. Despite his wealth and French economic prosperity, Napoleon III lost public support and popularity. So, in 1860, he began a series of reforms that allowed more individual freedoms in France.




1. What is the meaning of the word authoritarian in the passage?

A controlling people�s thoughts and actions

B writing books and stories

C being an expert on a subject

D being very wealthy




2. Which of the following statements best describes why Napoleon III probably changed the way he ruled France?

F He was getting old.

G He was unpopular and had lost public support.

H He had built as many railroads as he could.

I He used aluminum dinnerware.




3. According to the passage, in what year did Napoleon III die?

A 1808

B 1873

C 1860

D 1852




Passage 2 Named after architect Buckminster Fuller, buckyballs resemble the geodesic domes that are characteristic of the architect�s work. Excitement over buckyballs began in 1985, when scientists projected light from a laser onto a piece of graphite. In the soot that remained, researchers found a completely new kind of molecule! Continued on the next slide




Passage 2, continued Buckyballs are also found in the soot from a candle flame. Some scientists claim to have detected buckyballs in space. In fact, one suggestion is that buckyballs are at the center of the condensing clouds of gas, dust, and debris that form galaxies.




1. Which of the following statements correctly describes buckyballs?

A They are a kind of dome-shaped building.

B They are shot from lasers.

C They were unknown before 1985.

D They are named for the scientist who discovered them.




2. Based on the passage, which of the following statements is an opinion?

F Buckyballs might be in the clouds that form galaxies.

G Buckyballs are named after an architect.

H Scientists found buckyballs in soot.

I Buckyballs are a kind of molecule.




3. According to the passage, why were scientists excited?

A Buckyballs were found in space.

B An architect created a building that resembled a molecule.

C Buckyballs were found to be in condensing clouds of gas that form galaxies.

D A new kind of molecule was found.




Interpreting Graphics

Use the image of the periodic table below to answer the questions that follow.




1. Which of the following statements is correct for the elements shown?


A Lithium has the greatest atomic number.

B Sodium has the least atomic mass.

C Atomic number decreases as you move down the column.

D Atomic mass increases as you move down the column.



2. Which of the following statements best describes the outer electrons in atoms of the elements shown?

F The atoms of each element have 1 outer-level electron.

G Lithium atoms have 3 outer-level electrons, sodium atoms have 11, and potassium atoms have 19.

H Lithium atoms have 7 outer-level electrons, sodium atoms have 23, and potassium atoms have 39.

I The atoms of each element have 11 outer-level electrons.




3. The elements featured in the image belong to which of the following groups?

A noble gases

B alkaline-earth metals

C halogens

D alkali metals


chapter 12 section 1 arranging the elements...

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