1. Life on the edge
Valance electrons

2. ChemCatalyst
The three atoms below have similar reactivity and chemical behavior.
Where are these elements located on the periodic table?
What do you think might be responsible for their similar properties?
(cont.)
Unit 1 • Investigation III 2

3. (cont.)
Unit 1 • Investigation III 3

4. Answer Amount of neutrons, protons and electrons are different
Amount of electrons in the outermost ring is the same

5. The Big Question
What accounts for the similar chemistry of elements in the same group?
Unit 1 • Investigation III 5

6. You will be able to:
Give the number of valence electrons for an element.
Unit 1 • Investigation III 6

7. Changing… The number of protons, results in a new element
The number of neutrons, a more or less stable variation of the same element with different mass (formation of ISOTOPES)
The number of electrons…

8. What Bohr realized
That various chemical and physical properties of the elements can be traced to the arrangement of electrons in the orbits (shells).

9. Activity
Purpose: The various physical and chemical properties of the elements can be traced to the electrons. By studying electrons further we may be able to unlock the key to creating substances similar to gold. This lesson will reveal the arrangement of electrons within atoms.
Unit 1 • Investigation III 9

10. Procedure
Each student receives a copy of the handout and question worksheet. Work primarily on your own.
By using the information on the diagrams, answer the following questions
We will review the answers to the first 7 questions as a class, before finishing them out

12. Question 1
What do the atoms of all of Group 1 elements have in common?

13. Answer Question 1
A single electron in the outermost shell, orbit or ring

14. Question 2
How does the number of elements change as you move from atom to atom across a row?

15. Answer Question 2
The number of electrons in the outermost row increases by 1 as one moves across a row (period)

16. Question 3
How does the arrangement of electrons change as you move down the columns

17. Answer to 3
It seems like more rings are added

18. Question 4
How many shells of electrons does bromine have? How many electrons in bromine’s outermost shell?

19. Answer to 4
4, 7

20. Question 5
Predict the number of electrons in iodine’s outermost shell.

21. Answer to 5
7, same as all other elements in the group

22. Question 6
What happens to the electron count and the number of shells when you move from Neon (NE) to Sodium (Na)?

23. Answer to 6 One electron was added to a new ring
No room for the electron in the inner rings

24. Question 7
What group is thallium (Tl) in? How many electrons will it have in its outermost shell?

25. Answer to 7
Group 13 or 3a
3 electrons

26. Bohr and numbering shells
Bohr proposed that electrons could be found in different shells around the nucleus.
The letter “n” is referred to as the quantum number.
N also refers the position of the shell relative to the nucleus, with 1 being closest to the nucleus
Note the connection between the maximum quantum number and the period value for an element
Unit 1 • Investigation III 26

27. (cont.)
(cont.)
Unit 1 • Investigation III 27

28. The outermost shell of each drawing is called the valence shell.
(cont.)
The outermost shell of each drawing is called the valence shell.
The valence shell contains the valence electrons.
All other electrons are considered core electrons.
Unit 1 • Investigation III 28

29. Question 8
How many valence electrons does the element Se have? What about Na?

30. Answer to 8
Selenium has 6 valence electrons, sodium has 1

31. Question 9
How many valence electrons do the halogens have? How many do the noble gases have

32. Answer to 9
Halogens have 7
Nobles have 2 or 8

33. Question 10
How many CORE electrons does potassium (K) have? What about Germanium (Ge)?

34. Answer to 10
Oxygen and neon have 2 core electrons

35. Question 11
How many core electrons does oxygen have? What about Neon?

36. Answer to 11
18- k
28 Ge
28 Br

37. Question 12
If an atom has four shells containing electrons, what row is it in?

38. Answer to 12
IVA

39. Question 13
How many electron shells do you think Rb has? How many electrons will its outermost shell?

40. Answer to 13
5 shells
1 electron in in its outermost shell

41. Question 14
He pattern in the chart begins to vary between the element calcium and the element gallium. Explain what you think is going on?

42. Answer to 14
Have to start taking into account the transition metals

43. Question 15
Recall the card sort you did for the “Create a table ” lab. How were the valance electrons represented on these cards?

44. Answer to 15
The number of pegs or sticks attached to the circle

45. Valance electrons of transition metals
The arrangement of the electrons into shells determines the number of valance electrons
This gets complicated for the transition metals
As we shall soon talk about, each shell can be further divided into sub-shells
Specific sub-shells act as locations for valence electrons

46. Making Sense
Explain how you can determine the arrangement of an element’s electrons, from the element’s position on the periodic table.
Unit 1 • Investigation III 46

47. Making Sense
Generally arrangement depends on position in periodic table
Group determines valence electrons
Period determines # of shells/rings

48. If you finish early
Predict the electron arrangement of Scandium. Draw a picture of it. Explain your reasoning

49. Answer to If you finish earlySc
First( innermost shell) 2
2nd 8
3rd (8 +1 = 9)
4th 2

50. Wrap-Up
Electrons occupy different shells around the nucleus of an atom.
Each electron shell can hold a specific maximum number of electrons.
The valence electrons are in the outermost electron shell of an atom. Electrons that are not valence electrons are called core electrons.
(cont.)
Unit 1 • Investigation III 50

51. Elements with the same number of valence electrons have similar chemistry and are in the same group.
Unit 1 • Investigation III 51

52. Max number of electrons in each orbit (shell)
1st : 2 electrons
2nd: 8 electrons
3rd: 18 electrons
4th: 32 electrons

53. Check in
Provide the following information for the element with atomic number 34:
The elements name and symbol
The number of protons in the nucleus
The number of core electrons for this element
The number of valence electrons
The group number for this element
The names of other elements with similar chemical traits and properties