1. Notes #2: Periodic Trends
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Notes #2: Periodic Trends
WCHS Chemistry

2. Mendeleev Challenge +3+2+1
Main Point -
Elements in the same group (vertical column) have similar physical & chemical properties.
They follow a pattern as you move down the group!

3. Trend #1 - Atomic Radii (size)
Atoms get LARGER as you go DOWN a group.
WHY?? → More energy levels! (to hold more e-s)

4. TRENDS
More energy levels
Larger down a group

5. Trend #1 - Atomic Radii (size)
Atoms get LARGER as you go DOWN a group.
WHY?? → More energy levels! (to hold more e-s)
Atoms get SMALLER as you go ACROSS a period.
WHY?? → More protons = nucleus pulls harder on the electrons.

6. Smaller across a period Larger down a group
TRENDS
More energy levels
Smaller across a period
Nucleus pulls harder on e-s
Larger down a group

7. Trend #2 - Valence Electrons
electrons found in the outermost energy level
They are the only electrons used in bonding!
They come in contact with other atoms
Group # = # of valence electrons

8. Smaller across a period Larger down a group
EXCEPTION!
8e-
TRENDS
2e-
3e- 4e- 5e- 6e- 7e-
2e-
More energy levels
Smaller across a period
Larger down a group
Nucleus pulls harder on e-s

9. Trend #2 - Valence Electrons
electrons found in the outermost energy level
They are the only electrons used in bonding!
They come in contact with other atoms
Group # = # of valence electrons
EXCEPTION! →Helium (only has 2 e-s total!)
K = S = He = O = Ar = Sr = Sn =

10. Metals form CATIONS (+) Formed when atom GIVES electrons
Trend #3 - Ions
Metals form CATIONS (+)
Formed when atom GIVES electrons
Nonmetals form ANIONS (-)
Formed when the atom TAKES electrons

11. Smaller across a period Larger down a group
TRENDS
NON-METALS take e-s (-)
1e-
8e-
2e-
3e- 4e- 5e- 6e- 7e-
METALS give e-s (+)
2e-
More energy levels
Smaller across a period
Larger down a group
Nucleus pulls harder on e-s

12. Trend #4 - Reactivity IA Alkali metals - Extremely Reactive metals!
IIA Alkaline Earth metals - reactive
Transition metals
Rare Earth metals
VIIA Halogens - Extremely Reactive nonmetals!
VIIIA Noble Gases - Inert - doesn’t react!!!

13. Transitions from metalic to non-metalic properties
TRENDS
NON-METALS take e-s (-)
1e-
8e-
2e-
3e- 4e- 5e- 6e- 7e-
METALS give e-s (+)
2e-
More energy levels
Smaller across a period
Larger down a group
Nucleus pulls harder on e-s
Transitions from metalic to non-metalic properties
INERT!!
Most REACTVE NonMetals
REACTIVE
Rare on Earth
Most REACTIVE Metals

14. Trend #4 - Reactivity continued
Metals become more reactive as you go down the group.
Most reactive metal =

15. Transitions from metalic to non-metalic properties
TRENDS
NON-METALS take e-s (-)
1e-
8e-
2e-
3e- 4e- 5e- 6e- 7e-
METALS give e-s (+)
2e-
More energy levels
Smaller across a period
Larger down a group
More reactive down group
Nucleus pulls harder on e-s
INERT!!
Transitions from metalic to non-metalic properties
Most REACTVE NonMetals
REACTIVE
Rare on Earth
Most REACTIVE Metals

16. Trend #4 - Reactivity continued
Metals become more reactive as you go down the group.
Most reactive metal =
Francium!!
Nonmetals become more reactive as you go up the group.
Most reactive nonmetal =

17. Transitions from metalic to non-metalic properties
TRENDS
NON-METALS take e-s (-)
1e-
8e-
2e-
3e- 4e- 5e- 6e- 7e-
METALS give e-s (+)
2e-
More energy levels
Smaller across a period
Larger down a group
More reactive up group
Nucleus pulls harder on e-s
More reactive down group
INERT!!
Transitions from metalic to non-metalic properties
Most REACTVE NonMetals
REACTIVE
Rare on Earth
Most REACTIVE Metals

18. REACTIVITY VIDEOS