Chapter 5 – The Periodic Table

5.1 Organizing the Elements

Antoine Lavoisier (1743-1794)

• the Father of Modern Chemistry

• In 1789, he grouped the elements into categories

- metals

- nonmetals

- gases

- earths

• for 80 years scientists tried to classify elements, but no one way accounted for the variety of elements known

5.1 Organizing the Elements

Dmitri Mendeleev (1834-1907)

• a chemist and teacher

• by the 1860’s, there were 63 known elements

• used the game of solitaire as the inspiration for his organization of the elements

5.1 Organizing the Elements

• on each card, he listed the element’s name, mass and properties

• lined up cards in rows in order of increasing mass

• kept elements with similar properties in the same column

• the chart was periodic (repeating)

5.1 Organizing the Elements

periodic table – an arrangement of elements in columns, based on a set of properties that repeat from row to row

5.1 Organizing the Elements

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Which dot should replace the question mark?

1 2 3 4

5.1 Organizing the Elements

• Some elements would not fit in certain spots because they didn’t have the right mass and / or properties

• Mendeleev left gaps in the table

5.1 Organizing the Elements

• Mendeleev went on to give names to elements he predicted would be discovered and fill in the blanks

• Named a predicted element “eka-aluminum”

• Later an element was discovered that matched the properties of eka-aluminum. (named Gallium)

• With a periodic table the chemical behavior of elements can be explained and predicted

5.2 The Modern Periodic Table

• In the modern periodic table, elements are arranged by increasing atomic number (number of protons)

5.2 The Modern Periodic Table

• each row is called a period

• the number of elements per period varies because the number of available orbitals varies

5.2 The Modern Periodic Table

• each column is called a group

• the elements within a group have similar properties• the pattern of repeating properties is the periodic law

5.2 The Modern Periodic Table

HHydrogen

1

1.0079

atomic number

atomic mass

element symbol

element name

atomic mass unit (amu) – one twelfth the mass of a carbon-12 atom

5.2 The Modern Periodic Table

ClChlorine

17

35.453

What is the atomic mass of chlorine?

35.453 amu

Distribution of Chlorine

Isotopes in Nature

Isotope Percentage Atomic Mass

Chlorine-35 75.78% 34.969

Chlorine-37 24.22% 36.966

• the atomic mass is a weighted average of these values

5.2 The Modern Periodic Table

5.2 The Modern Periodic Table

• elements are first classified as solids, liquids, or gases

5.2 The Modern Periodic Table

• elements are then classified as to whether or not they occur naturally

• all but two elements in the first 92 elements occur naturally

5.2 The Modern Periodic Table

• then classified as metals, nonmetals, and metalloids

5.2 The Modern Periodic Table

• most of the elements are metals

- good conductors

- solid at room temperature (except Mercury)

- malleable and ductile

- some very reactive

5.2 The Modern Periodic Table

• transition metals are groups 3 through 12

• tend to form compounds with distinctive colors

5.2 The Modern Periodic Table

• other elements are called nonmetals

- poor conductors

- many are gases at room temperature

- the solids are brittle

- some are reactive, some aren’t

5.2 The Modern Periodic Table

• and still other elements are called metalloids

- properties of metals and nonmetals

- conductivity varies with temperature

5.2 The Modern Periodic Table

• elements become less metallic and more nonmetallic going across a period from left to right

5.2 The Modern Periodic Table

1. How did some ancient civilizations preserve their dead?

2. What are two types of information that scientists discover by examining mummies?

3. What evidence led forensic scientists to suspect Tutankhamen, also known as King Tut, might not have died from natural causes?

4. List features that scientists found in the bones of mummies in Chile.

5. What do forensic scientists suspect to be the causes of the features found in these mummies?

5.3 Representative Groups

Is hydrogen a metal?

It is not. Why, then, is it grouped with the metals in the periodic table?

It shares an electron configuration similar to other elements in Group 1

5.3 Representative Groups

The number of the A groups tells the number of valence electrons in an atom.

valence electron – an electron in the highest energy level of an atom

Elements in groups share properties because they have the same number of valence electrons

5.3 Representative Groups

In class assignment to be collected and graded:

Read pages 140-145. Each section discusses one of the A-groups on the periodic table. You are to do the following on a separate sheet(s) of notebook paper. All your pages are to be stapled and collected when you are finished.

1. Put a heading for each new section, it should contain both the A-Group name and number. Under each heading put:

2. The number of valence electrons

3. A list of the elements within the group (both name and symbol)

4. A comment on the reactivity of the elements within the group

5. Two elements or compounds containing the elements from the group and how they are used.

6. Two questions you formulate about each group based on what you have read.

When finished, do the questions on page 145 1-12 (complete sentences)

5.3 Representative Groups

Group 1A – Alkali Earth Metals

1. One valence electron

2. Found in nature as compounds

3. Reactivity increases going from top to bottom of group

4. Many react violently with water

5. Very soft (can cut with a knife)

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5.3 Representative Groups

Group 2A – Alkaline Earth Metals

1. Two valence electrons

2. Harder than Group 1A elements

5.3 Representative Groups

Group 3A – Boron Family

1. Three valence electrons

2. Aluminum is the most abundant metal in the Earth’s crust

5.3 Representative Groups

Group 4A – Carbon Family

1. Four valence electrons

2. Get more metallic as go down group

3. Most compounds in the body contain carbon (the exception is H2O)

4. Silicon is the 2nd most abundant element in the Earth’s crust

5.3 Representative Groups

Group 5A – Nitrogen Family

1. Five valence electrons

2. 78% of the atmosphere is nitrogen

5.3 Representative Groups

Group 6A – Oxygen Family

1. Six valence electrons

2. Oxygen is the most abundant element in the Earth’s crust

3. Sulfur was one of the first element’s discovered

5.3 Representative Groups

Group 7A – The Halogens

1. Seven valence electrons

2. All are highly reactive

3. Fluorine the most reactive, Chlorine a close second

4. React with metals to form compounds called salts

5.3 Representative Groups

Group 8A – The Noble Gases

1. Eight valence electrons, except Helium (has 2)

2. Colorless, odorless

3. Extremely unreactive

4. Used in “neon” lighting

5.3 Representative Groups