Discovering a Pattern

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

•His Periodic table showed that•Elements with similar properties occurred in a repeating pattern•There were gaps in its pattern •He could predict the properties of the missing elements

By 1886, all of the gaps had been filled and Mendeleev’s predictions were right.

Changing the Arrangement

• A few elements’ properties did not fit in the pattern of Mendeleev’s table.

• 1914: British scientist Henry Moseley found the atomic number of atoms.

• Elements arranged by atomic number fit the pattern in Mendeleev’s table.

Elements are arranged:

Vertically into Groups

Horizontally Into Periods

Why?

If you looked at one atom of every element in a group you would

see…

Each atom has the same number of electrons in it’s outermost shell.

• An example…

The group 2 atoms all have 2 electrons in their outer shells

Be (Beryllium)

Atom

Mg (Magnesium) Atom

• The number of outer or “valence” electrons in an atom effects the way an atom bonds.

• The way an atom bonds determines many properties of the element.

• This is why elements within a group usually have similar properties.

If you looked at an atom from each element in a period

you would see…

Each atom has the same number of electron holding shells.

An example…

The period 4 atoms each have 4 electron containing shells

K (Potassium)

AtomFe (Iron) Atom

Kr (Krypton)

Atom

4th Shell

Each group has distinct properties

• The periodic Table is divided into several groups based on the properties of different atoms.

The Periodic Table and Classes of Elements

• Elements are classified as metals, nonmetals, and metalloids based on number of electrons in outer shell

• an outer shell is considered complete when it contains 8 electrons

•The zigzag line on the periodic table can help you recognize which elements belong in which category.

Group 1: Alkali Metals

Alkali metals properties:

• metals• 1 electron in the outer level• very reactive• softness, color of silver, shininess, low density

Alkali Metals

Soft, silvery colored metals

Very reactive!!!

• found to the left of the zigzag line

• have few electrons in their outer energy level.

• shiny, ductile, malleable, and are good conductors of electric current and thermal energy.

Metals

Alkali Metals reacting with water:

• Li (Lithium)

• Na (Sodium)

• K (Potassium)

• Rb (Rubidium)

• Cs (Cesium)

What would you expect from Francium?!?!

Group 2: Alkaline-Earth Metals

Alkaline-earth metals properties:

• metals• 2 electrons in the outer level• very reactive, but less reactive than alkali metals• color of silver, higher densities than alkali metals

Alkaline Earth Metals

Silvery-White Metals

Fairly reactive

Many are found in rocks in the earth’s crust

Group 3–12: Transition Metals

Properties of Transition Metals vary widely but include:

• metals• 1 or 2 electrons in the outer level• less reactive than alkaline-earth metals• shininess, good conductors of electric current and thermal energy

Transition Metals

Malleable (easily bent/hammered into wires or sheets)

Most are good Conductors of electricity

How many things can you think of that have Transition Metals in

them?

Metalloids lie on either side of these “stairsteps”

They share properties with both metals and non-metals

Si (Silicon) and Ge (Germanium) are very important “semi-conductors”

• border the zigzag line

• 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.

Metalloids

What are semiconductors used in?

Nonmetals

Brittle

Do not conduct electricity

• to the right of the zigzag line

• have an almost complete set of electrons in their outer energy level.

•not shiny, ductile, or malleable, and poor conductors of electric current and thermal energy.

Nonmetals

Group 13: Boron Group

Group 13 properties:

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

Group 14: Carbon Group

Group 14 properties:

•one nonmetal, two metalloids, and two metals• 4 electrons in the outer level• reactivity varies among the elements• solids at room temperature

Group 15: Nitrogen Group

Group 15 properties:

•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)

Section 2 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 12

Section 2 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 12

Most are Poisonous

Fairly reactive

Halogens

Section 2 Grouping the Elements

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

Chapter 12

Chlorine Gas was used as a chemical weapon during World War I.

It was used by the Nazis in World War II.

Section 2 Grouping the Elements

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

Chapter 12

Unreactive

Gases at room temperature

Noble Gases

Jellyfish lamps made with noble gases artist- Eric Ehlenberger

Colors Noble Gases produce in lamp tubes:

• Ne (Neon): orange-red

• Hg (Mercury): light blue

• Ar (Argon): pale lavender

• He (Helium): pale peach

• Kr (Krypton): pale silver

• Xe (Xenon): pale, deep blue

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.

Lanthanide Series

Actinide Series

The Periodic Tables

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

Chapter 12

Concept Map

elements

periods

metals

electrons

nonmetals

periodic table

groups (families)

The Periodic TableChapter 12

The Periodic TableChapter 12

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

Chapter 12 Standardized Test Preparation

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.

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

Chapter 12 Standardized Test Preparation

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.

Chapter 12 Standardized Test Preparation

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.

Chapter 12 Standardized Test Preparation

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 Standardized Test Preparation

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 Standardized Test Preparation

2. A chemical company is preparing a shipment of 10 g each of four elements. Each element must be shipped in its own container that is completely filled with the element. Which container will be the largest?

F the container of aluminum

G the container of arsenic

H the container of germanium

I the container of silicon

Chapter 12 Standardized Test Preparation

ElementDensity (g/cm3)

Mass (g)

Aluminum 2.702 10

Arsenic 5.727 10

Germanium 5.350 10

Silicon 2.420 10

2. A chemical company is preparing a shipment of 10 g each of four elements. Each element must be shipped in its own container that is completely filled with the element. Which container will be the largest?

F the container of aluminum

G the container of arsenic

H the container of germanium

I the container of silicon

Chapter 12 Standardized Test Preparation

ElementDensity (g/cm3)

Mass (g)

Aluminum 2.702 10

Arsenic 5.727 10

Germanium 5.350 10

Silicon 2.420 10