Go to section

Physical Science Chapter 5.1-5.2Organizing the Elements

The Modern Periodic Table

Mrs. Pagar

Go to section

Pretest

1. Which of the following is a symbol for an element? a. Aluminumb. Alc. ald. AL

2. Is flammability a physical property or a chemical property?

3. What happens to the composition of matter during a physical change?

Chapter 5

Go to section

Pretest (continued)

4. What does the atomic number of an element represent?

5. Different isotopes of an element have different numbers of a. neutrons. b. electrons. c. protons. d. nuclei.

Chapter 5

Go to section

Pretest (continued)

6. True or False: Electrons in atoms occupy orbitals in energy levels.

7. Which element is more reactive, oxygen or nitrogen?

Chapter 5

Go to section

Interest Grabber

A Logical OrganizationThe ability to organize information in a logical way is a valuable skill. Have you ever noticed the way shoeboxes are arranged in a shoe store? Sometimes the shoeboxes are separated into a series of vertical stacks (or columns) by style. Within each stack, the shoes are arranged by size.

1. How is this system of organizing shoes useful? 2. Explain how a calendar organizes time. 3. Think of another example of how information is organized.

Section 5.1

Go to section

Reading Strategy

Summarizing

Section 5.1

a. Mendeleev arranged the elements in order of increasing mass so that elements with similar properties were in the same column.

b. Mendeleev used the properties of existing elements to predict properties of undiscovered elements.

c. The close match between Mendeleev’s predictions and the actual properties of new elements showed how useful his periodic table could be.

Go to section

a. Mendeleev’s Proposal Mendeleev arranged the elements in order of increasing

mass so that elements with similar properties were in the same column.

b. Mendeleev’s PredictionMendeleev used the properties of existing elements to

predict properties of undiscovered elements.

c. Evidence Supporting Mendeleev’s TableThe close match between Mendeleev’s predictions and the

actual properties of new elements showed how useful his periodic table could be.

Go to section

Mendeleev’s Table of Elements (1872)

Figure 3

Go to section

Periodic Table of Elements

Figure 7

Pretest Answers

1. Which of the following is a symbol for an element? a. Aluminumb. Alc. ald. AL

2. Is flammability a physical property or a chemical property?

3. What happens to the composition of matter during a physical change?

Chapter 5

Click the mouse button to display the answers.

a chemical property

It remains the same.

Chapter 5Pretest Answers (continued)

Click the mouse button to display the answers.

4. What does the atomic number of an element represent?

5. Different isotopes of an element have different numbers of a. neutrons. b. electrons. c. protons. d. nuclei.

the number of protons in an atom of the element

Chapter 5Pretest Answers (continued)

Click the mouse button to display the answers.

6. True or False: Electrons in atoms occupy orbitals in energy levels.

7. Which element is more reactive, oxygen or nitrogen?oxygen

Interest GrabberAnswers

1. How is this system of organizing shoes useful? This system makes it much easier for the salesperson to find the right shoe quickly.

2. Explain how a calendar organizes time.A calendar separates a year into months, then months into weeks, and then weeks into days.

3. Think of another example of how information is organized. Answers will vary, but may include a class schedule, train or bus schedule, or the aisles in a supermarket.

Section 5.1

Go to section

• Modern Periodic Table• - elements are arranged by increasing atomic number

( number of protons)• Period• - each row in a table. Period 1 has 2 elements. Periods 2 and

3 have 8 elements. Periods 4 and 5 have 18 elements. Period 6 has 32 elements. The number of elements per period varies because the number of available orbitals increases from energy level to energy level.

Go to section

• First energy level has only one orbital=> The one electron in a hydrogen atom and the two electrons in a helium atom can fit in this orbital.

• But one of the three electrons in a lithium atom ( 3 electrons) must be in the second energy level. That is why Lithium is the first element in Period 2.

• Sodium ( 11 electrons), the first element in Period 3, has one electron in its 3rd energy level.

• Potassium (19 electrons), the first element in Period 4, has one electron in its fourth energy level.

• This pattern applies to all elements in the first column on the table.

Go to section

• Each column on the periodic table is called a

• group.• The elements within a group have

similar properties. They have similar electronic configurations, which determines its chemical properties. This pattern of repeating properties is the

• Periodic law• Properties of elements repeat in a

predictable way when atomic numbers are used to arrange elements into groups. There are 18 groups in the periodic table. Some elements from Periods 6 and 7 have been placed below Period 7 so that the table is more compact

Go to section

• Four pieces of information: name of the element, symbol, atomic number, and its atomic mass

• Atomic mass • is a value that depends on the distribution of

an element’s isotopes in nature and the masses of those isotopes.

• Scientists assigned 12 atomic mass units to the carbon 12 atom which has 6 protons and 6 neutrons. An atomic mass unit ( amu) is defined as one twelfth the mass of a carbon-12 atom.

• There are two natural isotopes of chlorine, chlorine-35 and chlorine 37. Chlorine-35 has 17 protons and 18 neutrons. Chlorine -37 has 17 protons and 20 neutrons, more massive

Go to section

Go to section

• Elements are classified as metals, nonmetals and metalloids.• Metals• - are elements that are good conductors of electric current

and heat. On the periodic table below, they are represented by blue boxes( Figure 7 in book). Most metals are solids at room temperature (except Mercury), malleable, and ductile. Some metals are extremely reactive and some do not react easily. Gold remains shiny because it does not react with oxygen. Magnesium reacts with oxygen and quickly dulls.

Go to section

Periodic Table of Elements• Transition metals

• - elements that form a bridge between the electrons on the left and right sides of the table; metals in groups 3 through 12. Transition elements , such as copper and silver, were among the first elements discovered. Transition metals form compounds with distinctive colors.

Figure 7

Go to section

• Nonmetals• -are elements that are poor conductors of heat and electric

currents, normally represented by yellow boxes below ( Figure 7 in book).Non metals have low boiling points=> many are gases at room temperature. All gases in the periodic table are nonmetals. The nonmetals that are solid at room temperature tend to be brittle, easily shatters. Nonmetals vary as much in their chemical properties as they do in their physical properties. Some are extremely reactive, some hardly react at all, and some fall somewhere in between.

Go to section

• Metalloids• -elements with properties that fall between those of metals

and nonmetals, green boxes in Figure 7, in your book. • A metalloids ability to conduct electric current varies with

temperature. Pure silicon (Si) and Germanium( Ge) are good insulators at low temperatures and good conductors at high temperatures.

• Across a period from left to right, the elements become less metallic and more nonmetallic in their properties.

• The most reactive metals are on the left side and the most reactive nonmetals are on the right in Group 17.