The document discusses the history and development of the periodic table. It explains that in 1871, Mendeleev arranged elements based on increasing atomic mass and similar properties. In 1913, Moseley arranged elements based on increasing atomic number. The rest of the document discusses periodic trends in atomic radius, ionization energy, electronegativity, and reactivity based on an element's position in the periodic table. These trends help explain similarities in chemical and physical properties of elements within the same group.

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. 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
Behold!
The Pattern to the Periodic Chart

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:
1. Atomic Radius and Ionic Radius
2. Ionization Energy
3. Electronegativity
4. Reactivity
5. 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. How do electron configurations explain
why there is a big change in energy at
the red line?
Energy to Take Off Several Electrons

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.