Discovering a Pattern In 1869, Russian chemist Dmitri Mendeleev arranged the elements in order of...
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Transcript of Discovering a Pattern In 1869, Russian chemist Dmitri Mendeleev arranged the elements in order of...
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