1. Unit 7
Periodic Trends

2. Trends in Reactivity
Decreases
Increases
Decreases
Increases Li Na K

3. Most Reactive NonMetal
Trends in Reactivity
Decreases
Increases
Most Reactive NonMetal
Decreases
Increases F Li Na K Fr
Most Reactive Metal

4. Which element is more reactive?
Mg or Sr ?
K or Ca ?
Cl or I ?
Si or S ?

5. Arranging the Periodic Table
6.9
9.0
10.8
12.0
14.0
16.0
19.0
20.2
23.0
24.3
27.0
28.1
31.0
32.1
35.5
40.0
When elements are arranged in order of atomic mass, a pattern is found with repeating properties
Table was arranged to align elements with similar properties
Later realized each column also has same # of valence electrons
It is valence electron arrangement that determines properties of an element

6. Periodic Patterns: Elements in the same column have similar properties
So Mendeleev lined up elements with similar properties in the same column. Li
What else is similar about all elements in the same column? Na K

7. Arranging the Periodic Table
Later realized each column also has same # of valence electrons
It is valence electron arrangement that determines properties of an element

8. Mendeleev
Mendeleev left blank spaces where no elements matched properties
Mendeleev predicted the existence of undiscovered elements
Mendeleev predicted the properties of these undiscovered elements

9. Atomic Attractions What holds the earth in its orbit?
What holds the electrons in the atom?

10. Trends in Attractions Moving down a column Focus onLi
Focus on
attractions between
nucleus and
valence electrons Na K

11. Trends in Attractions Moving down a column Which elementLi
Which element
has a stronger hold
on its
valence electron? Na K

12. Trends in Attractions Moving down a column Close to nucleusLi
Strongest
Attraction Na
Far from nucleus K
Weakest
Attraction

13. Trends in Attractions Moving down a column Least ShieldingLi
Strongest
Attraction Na
Most Shielding K
Weakest
Attraction

14. Trends in Attractions Moving down a column Li As you move
Strongest
Attraction
As you move
Down a column,
the attraction ……. Na K
Weakest
Attraction

15. Trends in Attractions
Moving across a row C N O

16. on its valence electrons?
Trends in Attractions
Moving across a row C N O
Which element
has a stronger hold
on its valence electrons?
Same Energy Level
(Distance)
Same Amount of
Shielding

17. As you move across a row, the attraction …….
Trends in Attractions
Moving across a row
Strongest
Attraction
Weakest
Attraction C N O 6
Protons 7
Protons 8
Protons
As you move across a row, the attraction …….

18. Which atom is bigger? F or Cl ? Li Na Going down any column,
the atoms get bigger because you
are adding energy levels K

19. Which atom is bigger? C or O ? C N O Moving across any row, the atoms6
Protons 7
Protons 8
Protons
Moving across any row, the atoms
Get smaller because energy level
Is same, but attraction increases

20. Trends in Sizes of Atoms

21. Which element is bigger?
Mg or Sr ?
K or Ca ?
Cl or I ?
Si or S ?

22. Trends in Sizes of Ions
What happens to the size of an atom when an electron is removed? Why?

23. Trends in Sizes of Ions
What happens to the size of an atom when an electron is added? Why?

24. Trends in Sizes of Ions of Different Elements
Who is bigger K or Cl ?
Compare the two ions
Protons Electrons 19 17 K+ 18
Cl- 18

25. Which element is bigger?
Mg or Mg+2 ?
Se or Se-2
Ca or Ca+2
Fe+2 or Fe+3
* O-2 and F-1
* Sr+2 and Br-1
* Look at electron – proton breakdown and think tug-of-war

26. Go to Ionization Energy Worksheet

27. Exceptions to the trends in Ionization Energy

28. What Elements have the highest Ionization Energy ? Why?

29. What happens to IE as you move across a row?
What would a graph look like of IE?
Ionization Energy
Li Be B C N O F Ne

30. Does the graph for row 2 appear as the trends predict?

31. What Groups have higher ionization energies than expected?

32. Draw Orbital Notation for:
Group II: Mg
Group V: N
d10 Group: Zn
Why do you think these groups have higher ionization energies than expected?

33. Electron Affinity
Energy change that occurs when you add an electron to an atom
What charge will it have ? - e- +
Will ion be bigger or smaller ?

34. Trends in Electron Affinity
What Groups would want e-’s?
What Groups would not want e-’s?
Turn to page 182 in text
What do you first notice about affinities?

35. Energy and Chemical Reactions
All chemical reactions are accompanied by a change in energy
If energy is taken in / absorbed / added / required
Reaction is endothermic
Energy change has positive sign (system is gaining energy)
Example:
Water + energy  Hydrogen + Oxygen
Energy term will go on left side of equation

36. Energy and Chemical Reactions
If energy is given off / released / produced
Reaction is exothermic
Energy change has negative sign (system is losing energy)
Example:
CH4 + oxygen  energy
CO2
H2O
Energy term will go on right side of equation

37. You turn: Label each reaction as endo or exothermic
When water changes from a liquid to a gas, it requires 44 kJ of energy.
You body reacts glucose with oxygen to produce CO2 and H2O. The energy change for this process is kJ.
The melting of ice.
KMnO kJ  K+ + MnO4-
The burning of coal.

38. Writing Equations with energy
Show the removal of an e- from magnesium
Show the addition of an e- to magnesium
Show the addition of an e- to bromine

39. Review Practice Ca, Na, Hg, Al, Si, S, Cl, Cl+
Arrange the above in order of increasing size
Arrange the above in order of increasing I.E.
Which would you predict to have a positive E.A?
Which would you expect to release the most energy when an electron is added to it?
Only include for #1