Discovering a Pattern

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(No Transcript)
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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
  Mendeleevs predictions were right.

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Changing the Arrangement

• A few elements properties did not fit in the
  pattern of Mendeleevs table.
• 1914 British scientist Henry Moseley found the
  atomic number of atoms.
• Elements arranged by atomic number fit the
  pattern in Mendeleevs table.

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Elements are arranged
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Why?
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If you looked at one atom of every element in a
group you would see
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Each atom has the same number of electrons in
its outermost shell.

• An example

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The group 2 atoms all have 2 electrons in their
outer shells
Be (Beryllium) Atom
Mg (Magnesium) Atom
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• 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.

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If you looked at an atom from each element in a
period
you would see
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Each atom has the same number of electron holding
shells.
An example
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The period 4 atoms each have 4 electron
containing shells
4th Shell
K (Potassium) Atom
Kr (Krypton) Atom
Fe (Iron) Atom
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Each group has distinct properties

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

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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.

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Group 1 Alkali Metals

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

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http//www.lyon.edu/webdata/Users/DMcDowell/GenChe
m/alkalishow.html
Alkali Metals Soft, silvery colored metals Very
reactive!!!
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Metals

• 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.

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Alkali Metals reacting with water

• Li (Lithium)
• Na (Sodium)
• K (Potassium)
• Rb (Rubidium)
• Cs (Cesium)

What would you expect from Francium?!?!
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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

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Alkaline Earth Metals
Silvery-White Metals Fairly reactive Many are
found in rocks in the earths crust
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Group 312 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

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Transition Metals
Malleable (easily bent/hammered into wires or
sheets)
Most are good Conductors of electricity
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How many things can you think of that have
Transition Metals in them?
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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
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Metalloids

• 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.

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What are semiconductors used in?
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Nonmetals
Brittle Do not conduct electricity
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Nonmetals

• 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.

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Group 13 Boron Group

• Group 13 properties
• 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
• 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 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)

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Section 2 Grouping the Elements
Chapter 12
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)

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Section 2 Grouping the Elements
Chapter 12
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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Halogens
Most are Poisonous Fairly reactive
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Section 2 Grouping the Elements
Chapter 12
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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Chlorine Gas was used as a chemical weapon during
World War I. It was used by the Nazis in World
War II.
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Section 2 Grouping the Elements
Chapter 12
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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Noble Gases
Unreactive Gases at room temperature
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Jellyfish lamps made with noble gases artist-
Eric Ehlenberger
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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

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Group 312 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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Lanthanide Series
Actinide Series
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The Periodic Tables
Chapter 12
Concept Map
Use the terms below to complete the concept map
on the next slide.
elements periods metals electrons nonmetals periodic table groups (families)

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The Periodic Table
Chapter 12
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The Periodic Table
Chapter 12
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Standardized Test Preparation
Chapter 12
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.
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Standardized Test Preparation
Chapter 12
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.
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Standardized Test Preparation
Chapter 12
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.
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Standardized Test Preparation
Chapter 12
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.
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Standardized Test Preparation
Chapter 12
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
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Standardized Test Preparation
Chapter 12
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
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Standardized Test Preparation
Chapter 12
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
Element Density (g/cm3) Mass (g)
Aluminum 2.702 10
Arsenic 5.727 10
Germanium 5.350 10
Silicon 2.420 10
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Standardized Test Preparation
Chapter 12
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
Element Density (g/cm3) Mass (g)
Aluminum 2.702 10
Arsenic 5.727 10
Germanium 5.350 10
Silicon 2.420 10