1. The Periodic Table
TRENDS

2. History of the Periodic Table
1871 – Mendeleev arranged the elements according to:
1. Increasing atomic mass
2. Elements w/ similar properties were put in the same row.
1913 – Moseley arranged the elements according to:
1. Increasing atomic number
2. Elements w/ similar properties were put in the same column.

5. Review of Electron Configuration
Increasing energy 1s 2s 3s 4s 5s 6s 7s 2p 3p 4p 5p 6p 3d 4d 5d 7p 6d 4f 5f
Review of Electron
Configuration

6. Periodic Table & Electron Configuration

7. Periodic Groups
Elements in the same column have similar chemical and physical properties.
These similarities are observed because elements in a column have similar e- configurations (same amount of electrons in outermost shell).

8. Know the Group Names

9. Periodic Trends Trends we’ll be looking at:
Atomic Radius and Ionic Radius
Ionization Energy
Electronegativity
Reactivity
Metallic Character

10. Atomic Radius Atomic Radius – size of an atom
(distance from nucleus to outermost e-).

11. Atomic Radius Trend
Group Trend – As you go down a column, atomic radius increases.
As you go down, e- are filled into orbitals (energy levels) that are farther away from the nucleus (attraction not as strong).
Periodic Trend – As you go across a period (L to R), atomic radius decreases.
As you go L to R, e- are put into the same energy level, but more p+ and e- total (more attraction = smaller size).

12. Ionic Radius
Ionic Radius -
size of an atom when it is an ion.

13. Ionic Radius Trend
Metals – lose e-, which means more p+ than e- (more attraction) SO…
Ionic Radius < Neutral Atomic Radius
Nonmetals – gain e-, which means more e- than p+ (not as much attraction) SO…
Ionic Radius > Neutral Atomic Radius

14. Ionic Radius Trend
Group Trend – As you go down a column, atomic radius increases.
Periodic Trend – As you go across a period (L to R), atomic radius decreases.

15. Ionization Energy
Ionization Energy – energy needed to remove outermost e-.

16. Ionization Energy
Group Trend – As you go down a column, ionization energy decreases.
As you go down, atomic size is increasing (less attraction), so easier to remove an e-.
Periodic Trend – As you go across a period (L to R), ionization energy increases.
As you go L to R, atomic size is decreasing (more attraction), so more difficult to remove an e-
(also, metals want to lose e-, but nonmetals do not).

17. Energy to Take Off Several Electrons
How do electron configurations explain why there is a big change in energy at the red line?

18. Electronegativity
Electronegativity- tendency of an atom to attract e-.

19. Electronegativity Trend (really electron affinity)
Group Trend – As you go down a column, electron affinity decreases.
As you go down, atomic size is increasing, so less attraction of electrons to the nucleus.
Periodic Trend – As you go across a period (L to R), electron affinity increases.
As you go L to R, atomic size is decreasing, so the electrons are more attracted to the nucleus.

20. Reactivity Reactivity – tendency of an atom to react.
Metals – lose e- when they react, so metals’ reactivity is based on lowest Ionization Energy (bottom/left corner)
Low I.E = High Reactivity.
Nonmetals – gain e- when they react, so nonmetals’ reactivity is based on high electronegativity (upper/right corner).
High electronegativity = High reactivity

21. Metallic Character Properties of a Metal –
Easy to shape (malleable); many are ductile (can be pulled into wires)
Conduct electricity and heat
Shiny
Group Trend – As you go down a column, metallic character increases (because ionization energy decreases).
Periodic Trend – As you go across a period (L to R), metallic character decreases (because ionization energy decreases) (L to R, you are going from metals to non-metals).

22. Do This…
Based on these trends, can you describe some properties of the following groups?
Alkali
Alkaline
Halogens
Noble Gases
Also, be able to identify metals, transition metals semi-metals, and non-metals and know some properties of each.