1. Periodic Table Determining Shells and Valence Electrons
2008
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2. Periods Each row is called a “period”
The elements in each period have the same number of shells
1st Period = 1 Shell(2 Electrons)
2nd Period = 2 Shells(8 Electrons)
3rd Period = 3 Shells(18 Electrons)
4th Period = 4 Shells(32 Electrons)

3. Groups Group 8 = 8 electrons Group 1 = 1 electron
Except for He, it has 2 electrons
Group 2 = 2 electrons
Each column is called a “group”
3, 4, 5, 6, 7
Each element in a group has the same number of electrons in their outer orbital, also known as “shells”.
The electrons in the outer shell are called “valence electrons”

4. Transition Metals
Transition Metals have slightly different rules for shells and valence electrons.
This is something you will learn about in High School Chemistry.
You wrote them on your P.T., as cations and anions.

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

6. Drawing Bohr Models Draw the nucleus.
Write the number of neutrons and the number of protons in the nucleus.
Draw the first energy level.
Draw the electrons in the energy levels according to the rules below. Make sure you draw the electrons in pairs.
Keep track of how many electrons are put in each level and the number of electrons left to use.

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 tableNe
Name the element.
Number of shells ?
Valence electrons ?

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

10. H
Name the element.
Number of shells ?
Valence electrons ?

11. H Name the element. Number of shells ? Valence electrons ? Hydrogen
1st Period = 1 shell
1st Group = 1 valence
electron

12. Write your answers on your table.Be
Name the element.
Number of shells ?
Valence electrons ?

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

14. Write your answers on your paper.
Name the element.
Number of shells ?
Valence electrons ?

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

16. Write your answers on your paper.K
Name the element.
Number of shells ?
Valence electrons ?

17. Write your answers on your paper.K
Name the element.
Number of shells ?
Valence electrons ?
Potassium
4th Period = 4 shells
1st Group = 1 valence
electron

18. Write your answers on your paper.He
Name the element.
Number of shells ?
Valence electrons ?

19. Write your answers on your paper.He
Name the element.
Number of shells ?
Valence electrons ?
Helium
1st Period = 1 shell
8th Group = 2 valence
electrons
Helium is the exception in Group 8.
Since it has just one shell, that shell can only fit 2 electrons instead of 8.
It is in this group because all the elements have a full outer shell.

20. Warm Up For the following elements list: Name of the element
#of shells
Total # of electrons
#of valence electrons Mg N Ar B Na H

21. Mg For the following elements list: Name of the element-Magnesium
#of shells-3
Total # of electrons-12
#of valence electrons-2

22. N For the following elements list: Name of the element-Nitrogen
#of shells-2
Total # of electrons-7
#of valence electrons-5

23. Ar For the following elements list: Name of the element-Argon
#of shells-3
Total # of electrons-18
#of valence electrons-8

24. B For the following elements list: Name of the element-Boron
#of shells-2
Total # of electrons-5
#of valence electrons-3

25. Na For the following elements list: Name of the element-Sodium
#of shells-3
Total # of electrons-11
#of valence electrons-1

26. H For the following elements list: Name of the element-Hydrogen
#of shells-1
Total # of electrons-1
#of valence electrons-1

27. www.middleschoolscience.com 2008
How to Draw Lewis Structures
Also referred to electron dot configurations
2008

28. Lewis Structures Find your element on the periodic table.
Determine the number of valence electrons.
This is how many electrons you will draw.

29. Lewis Structures Find out which group (column) your element is in.
This will tell you the number of valence electrons your element has.
You will only draw the valence electrons.

30. Groups - Review Group 8 = 8 electrons Group 1 = 1 electron
Except for He, it has 2 electrons
Group 2 = 2 electrons
Each column is called a “group”
3, 4, 5, 6, 7
Each element in a group has the same number of electrons in their outer orbital, also known as “shells”.
The electrons in the outer shell are called “valence electrons”

31. C Lewis Structures Write the element symbol.
Carbon is in the 4th group, so it has 4 valence electrons.
Starting at the right, draw 4 electrons, or dots, counter-clockwise around the element symbol. C

32. C Lewis Structures Check your work.
Using your periodic table, check that Carbon is in the 4th group.
You should have 4 total electrons, or dots, drawn in for Carbon. C

33. C Lewis Structures On your paper, try these elements on your own: H PCa Ar Cl Al C

34. H Lewis Structures On your worksheet, try these elements on your own:P Ca Ar Cl Al H

35. P Lewis Structures On your worksheet, try these elements on your own:Ca Ar Cl Al P

36. Ca Lewis Structures On your worksheet, try these elements on your own:P Ca Ar Cl Al Ca

37. Ar Lewis Structures On your worksheet, try these elements on your own:P Ca Ar Cl Al Ar

38. Cl Lewis Structures On your worksheet, try these elements on your own:P Ca Ar Cl Al Cl

39. Al Lewis Structures On your worksheet, try these elements on your own:P Ca Ar Cl Al Al

41. Atoms Ions and isotopes

42. When atoms lose or gain an electron, the atom turns into an ion.
When an atom gains or lose a neutron, it is called an isotope.
When either of these two things happen, then we no longer use the term element to describe the atoms.
Remember, it is the number of protons that determines what type of atom it is.

43. Recreate and complete the chart below
Atom
Atomic Symbol
Atomic Number
#of Protons
Atomic Mass
Rounded
# of Neutrons
#of Electrons
Lithium
Lithium Ion
(Loses an electron)
Beryllium
Isotope

44. Recreate and complete the chart below
Atom
Atomic Symbol
Atomic Number
#of Protons
Atomic Mass
Rounded
# of Neutrons
#of Electrons
Lithium
Lithium Ion
(Loses an electron)
Beryllium
Isotope Li 3 3 7 4 3
Li+ 3 3 2 7 4 Be 4 4 9 5 4
Be-8 4 4 8 4 4

45. Write a definition for ion
Write a definition for isoptope

46. When atoms come together, they form molecules and compounds.
What is the difference between a compound and a molecule?
A molecule is formed when two or more atoms join together chemically. A compound is a molecule that contains at least two different elements.
*All compounds are molecules but not all molecules are compounds.

47. Molecular hydrogen (H2), molecular oxygen (O2) and molecular nitrogen (N2) are not compounds because each is composed of a single element. Water (H2O), carbon dioxide (CO2) and methane (CH4) are compounds because each is made from more than one element.
The smallest bit of each of these substances would be referred to as a molecule. For example, a single molecule of molecular hydrogen is made from two atoms of hydrogen while a single molecule of water is made from two atoms of hydrogen and one atom of oxygen.

48. How do molecules form?
Two ways (Well, actually three, but we are only going to look at two.)
As it turns out, atoms bond together for a very simple reason:
Atoms like to have full valence shells!

49. 1st way- Covalent Bond:
This is when two atoms SHARE an electron.
2 hydrogen atoms equally share electrons to form a covalent bond.
Each covalent bond is represented by a line in the Lewis dot structure, so the molecule shown above would be represented as  H-H and the chemical formula would be H2 (the subscript indicates the number of atoms of a single type in a compound). 

50. Atoms can form multiple covalent bonds if they need more than one electron to complete their valence shells.  Oxygen, for example, bonds with itself to form 2 bonds between the atoms (since each atom needs to share 2 electrons).  The Lewis dot structure would be
showing that each oxygen atom has 4 shared electrons (2 per bond) and 4 unshared electrons, giving each a total of 8 and filling the valence shells. If two atoms have equal electron affinities they form covalent bonds.

51. 2nd way- Ionic Bonding
So, if one atom has a much greater affinity for electrons than another, the two may form an ionic bond. 
For sodium to have a full valence shell it can do one of 2 things: pick up 7 new electrons (which is a very difficult thing to do) or give up one.  If sodium gave up the 1 electron in its 3rd shell, this shell would now be empty and the 2nd shell (which is filled with 8 electrons) would become its valence shell.  Thus chlorine and sodium are a perfect match for each other. 

52. When the chlorine atom gets close enough to the sodium atom, it strips away the sodium's electron and the two ions formed attract each other because of their opposite charges.  Using the Lewis dot structure to represent the reaction we would write:

53. Covalent share with Non-Metals
The compounds which form Covalent Bonds are those that result from a sharing of electrons between Non-Metal Elements (Groups IIIA through VIA of the Periodic Table and Hydrogen (Group IA).
Ionic bonds share with metals
The compounds which form Ionic Bonds are those that result from an exchange of electrons between Metals (Groups IA, IIA and IB through VIIIB of the Periodic Table) and the Halogens (Group VIIA).

54. H2 H H H

55. NaCl
Na Cl
Na Cl1-

56. H20 O H O H H

57. Na 2O O Na Na
Na 21+ O 2-

58. CaCl2 Cl Cl Ca
Ca2+
Cl21-

59. C H4 C H H H H C H

60. CO2 O C
O=C=O

61. CHCl3 C H Cl H H H H H