1. What are we learning?
C.5B: Use the Periodic Table to identify and explain the properties of chemical families, including alkali metals, alkaline earth metals, halogens, noble gases, and transition metals.
C.5C: Use the Periodic Table to identify and explain periodic trends, including atomic ionic radii, electronegativity, and ionization energy. (BEGIN)

2. In your science notebook answer the following questions:
What chemical trend do you notice as each alkali metal is reacting with water? Make sure to use the words group, alkali metal, and reactivity.
Predict what would happen if Rb, Cs, and Fr were added to water.

3. Let’s watch the video to check your answer!

4. Valence Electrons

5. Valence Electrons
Valence electrons are the number of electrons in the outermost energy level.
All elements within a group have the same number of valence electrons
These electrons are available to be lost, gained, or shared in the formation of chemical compounds.
Found in the s and p orbitals of the highest energy level.
Often located in incompletely filled energy levels.

6. How do I find the number of Valence Electrons?
To find the number of valence electrons, underline the largest number as often as it occurs and add the superscripts.
Example: Cl – 1s2, 2s2, 2p6, 3s2, 3p5 – 7 valence electrons
Example: Mg - 1s2, 2s2, 2p6, 3s2 – 2 valence electrons
Example: Kr – 1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d10, 4p6 – 8 valence electrons
Example: U – 1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d10, 4p6, 5s2, 4d10, 5p6, 6s2, 4f14, 5d10, 6p6, 7s2, 5f4 – 2 valence electrons

7. Shortcut to finding Valence Electrons!
Group valence electron Group valence electrons Group valence electrons Group valence electrons Group valence electrons Group valence electrons Group valence electrons Group valence electrons

8. WARNING
there is no shortcut for finding valence electrons for transition or inner-transition metals
The number of valence electrons for elements from Groups 3-12 can have different values based on the conditions of chemical reactions. This is also true for a small number of the metals in Groups 13-16

9. Reactivity of groups
Elements in the same group/family have the same number of valence electrons.
If you’ll remember from last class, elements in the same group have the similar physical and chemical properties; they react the same way (think alkali metal demo). This has to do with the number of valence electrons!

10. Oxidation Numbers
Remember that all atoms want to have a full outermost energy level of 8?.....

11. Oxidation Numbers
The electrical charge resulting from atoms gaining or losing electrons to fill their outermost s and p orbitals.
All uncombined elements have an oxidation number of zero (0)
Metals lose electrons and have (+) oxidation numbers; nonmetals gain electrons and have (–) oxidation numbers
All Noble Gases have an oxidation number of zero (0).

12. Ions
Ion – a charged particle or molecule created through the loss or gain of valence electrons
Cation – positively charged particle or molecule created through the loss of valence electrons as a result of ionization
Anion – negatively charged particle or molecule created through the gain of valence electrons as a result of electronegativity

13. Making atoms! Make a neutral lithium atom.
How many protons should it have?
How many electrons?
In order for Li to be stable, would it be easier to add 7 electrons or take away 1?
What would be Li’s oxidation number?

14. Making atoms! Make a neutral atom of fluorine.
How many protons? How many electrons?
Should you add valence electrons or take away to fill it’s outermost s and p orbital?
What would be it’s oxidation number?

15. Make models of each of the following atoms and determine it’s oxidation number. Record answers in your notebook.
Element
Group #/Name
# Valence Electrons
Oxidation Number
Lithium
Sodium
Beryllium
Magnesium
Boron
Aluminum
Oxygen
Sulfur
Fluorine
Chlorine
Neon
Argon
Explain trends you see going down the group and across the period. Predict oxidation numbers
for nitrogen, strontium, and Iodine.

16. In your notebook…
Explain why metals tend to have positive oxidation numbers.
Explain why non metals tend to have negative oxidation numbers.
Explain why the noble gases have an oxidation number of zero.

18. Oxidation Number
Typically, it’s the number of electrons needed to be lost or gained in order to complete a stable electron configuration. (How many electrons do I need to gain or lose in order to have a full outermost energy level of 8?)
metals need to lose electrons. They have (+) oxidation numbers
nonmetals need to gain electrons. They have (–) oxidation numbers
All Noble Gases have an oxidation number of 0.

19. How do I find an element’s Oxidation Number?
Oxygen, for example, has 6 valence electrons. It needs to gain two electrons in order to get 8… Its oxidation number typically is -2.
Aluminum has 3 valence electrons. It needs to lose three electrons… Its oxidation number typically is +3.

20. Making sense of valence electrons and oxidation numbers!

21. Group 1- Alkali Metals
Alkali metals are the most reactive metals because they only have one valence electron and it is “easier” for them to lose that one electron.
They have similar chemical and physical properties because they have 1 valence electron.
In our demo, all the alkali metals reacted with water. (reactivity = chemical property)

22. Group 17 - Halogens
Halogens are the most reactive nonmetal since they have 7 valence electrons. It is easier for them to gain one electron.
They have similar chemical and physical properties because they ALL have 7 valence electrons

23. Noble Gases
Noble Gases are non reactive since they have all their valence electrons. They do not need to gain or lose any electrons.
They have the maximum number of electrons in their outermost energy levels.

24. On your periodic table, let’s label the valence electrons and oxidation number trends!
Valence electrons: Oxidation #:

25. Review Time! Which group has 2 valence electrons?
What is that group’s special name?

26. Review Time!
Which group is NONREACTIVE?
Why?

27. Review time!
Would Cesium react (have similar chemical properties) like Lithium or Barium?
Why?

28. Review Time!
A new element was found!!! They have named it Gonzalium…It has 113 protons.
Which group would it be in?
Which elements would have similar chemical and physical properties like Gonzalium?

29. What did we learn?
C.5B: Use the Periodic Table to identify and explain the properties of chemical families, including alkali metals, alkaline earth metals, halogens, noble gases, and transition metals.
C.5C: Use the Periodic Table to identify and explain periodic trends, including atomic ionic radii, electronegativity, and ionization energy. (BEGIN)

30. Exit Ticket:
Explain why elements in the same group have similar chemical and physical properties. Make sure to use valance electrons and oxidation numbers when explaining.