1. Adapted by Mrs. Hunt from Mrs. LaRosa www.middleschoolscience.com 2008
Introduction to the
Periodic Table of Elements
Adapted by Mrs. Hunt from Mrs. LaRosa
2008
All images are from

2. OBJECTIVES What should you be able to do at the end of class?
Describe the basic organization of the periodic table of elements.
Use the periodic table to determine the number of electron shells and valence electrons of an element.

3. What is the Periodic Table of Elements?
The Periodic Table of Elements is a way of organizing the elements in relation to each other so it is easy to find elements that have similar properties.
Why is that helpful?
It allows scientists to make predictions and explain events.

4. Periods Each row is called a “period”
The elements in each period have the
same number of electron shells
1st Period = 1 Shell
2nd Period = 2 Shells
3rd Period = 3 Shells
4th Period = 4 Shells
Hint:
A period comes at the end of a sentence--a horizontal line.

5. Groups or Families 1 Group 8 = 8 electrons Group 1 = 1 electron
Except for He, it has 2 electrons
Group 2 = 2 electrons 1 18
Each column is called a “group” or family. 2
Each element in a group has the same number of electrons in its outer orbital, also known as its outer shell.
The electrons in the outer shell are called “valence electrons.”
Hint: Your Family tree is vertical.

6. Determine the number of shells and the number of valence electrons for:
Carbon - C
2nd Period = 2 shells
14th Group =
4 valence
electrons

7. Determine the number of shells and the number of valence electrons for:
Sodium - Na
3rd Period = 3 shells
1st Group =
1 valence
electron

8. Write your answers on your notes.Ne
Name the element.
Number of shells ?
Valence electrons ?

9. Write your answers on your handout.
Ne - Neon
Name the element.
Number of shells ?
Valence electrons ?
Neon
2nd Period = 2 shells
8th Group = 8 valence
electrons 1

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Atom Models
There are two models of the atoms we will be using in class.
Bohr Model
Lewis Dot Structure
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Bohr Model
The Bohr Model shows all of the particles in the atom.
In the center are circles. Each circle represents a single neutron or proton. Protons should have a plus or P written on them. Neutrons should be blank or have an N.
In a circle around the nucleus are the electrons. Electrons should have a minus sign or an e. - + + -
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12. Electrons have special rules….
You can’t just shove all of the electrons into the first orbit of an electron.
Electrons live in something called shells or energy levels.
Only so many can be in any certain shell.
The electrons in the outer most shell of any element are called valance electrons.
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Nucleus
1st shell
2nd shell
3rd shell
Adapted from
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So let’s try it….
How to draw a Lithium atom
First, look at the Periodic Table
Second, determine the number of protons the atomic number)
Then determine the number of neutrons (Atomic mass – atomic number)
Then determine the number of electrons the atomic number) 3 Li
Lithium 7
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So let’s try it….
Protons = 3 3 Li
Lithium 7 - + + + - -
Electrons = 3
2 in the 1st shell, 1 in the 2nd shell
Neutrons = 4
(7-3=4)
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Lewis Dot Structure
The Lewis Dot Structure is a bit different from the Bohr model.
It only shows the element symbol and it’s outer most electron shell. + - • O • • •
• •
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How to…
Write the symbol.
Start on the right hand side, working your way around the symbol.
Try Lithium
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18. Draw both the Bohr Diagram & Lewis Dot Structure
Name the element.
Number of shells ?
Valence electrons ?

19. Draw both the Bohr Diagram & Lewis Dot Structure
Name the element.
Number of shells ?
Valence electrons ?
Hydrogen
1st Period = 1 shell
1st Group = 1 valence
electron

20. Draw both the Bohr Diagram & Lewis Dot StructureBe
Name the element.
Number of shells ?
Valence electrons ?

21. Write your answers on your notes.Be
Name the element.
Number of shells ?
Valence electrons ?
Beryllium
2nd Period = 2 shells
2nd Group = 2 valence
electrons

22. Draw both the Bohr Diagram & Lewis Dot Structure
Name the element.
Number of shells ?
Valence electrons ?

23. Write your answers on your handout.
Name the element.
Number of shells ?
Valence electrons ?
Sulfur
3rd Period = 3 shells
6th Group = 6 valence
electrons 1