1. Periodic Table
Chapter 4

2. History of the Periodic Table
Dmitri Mendeleev wrote the first periodic table.
He arranged elements in order of atomic mass.
He noticed repeating properties.

3. Mendeleev’s periodic table

4. Moseley’s periodic table
Moseley rearranged the elements by atomic number.

5. Organization of the p.t. There are 18 groups or families (columns).
All elements in a group have the same number of outer level (valence) electrons.
There are 7 periods (rows).
All elements in a period have electrons on the same energy level.

6. Why? Group 1 metals Called alkali metals.
They all react violently with nonmetals.
They have 1 valence electron which they lose very easily.
Li is the least reactive, Fr is the most reactive
They are all soft
They are not found in nature because they are so reactive.
Why?

7. Group 2 metals Called Alkaline Earth Metals
They have 2 valence electrons.
They are harder and less reactive than group 1 metals.

8. Why? Group 17 Called halogens Most reactive nonmetals
They all have 7 valence electrons
They react with metals to form “salts”
Why?

9. Why? Group 18 Noble gases They don’t react
They have 8 valence electrons (except Helium)
This is a full outer level
Why?

10. Metals Most elements are metals
Metals are good conductors of heat and electricity
Metals are ductile (can be squeezed into a wire)
Metals are malleable (can be hammered or bent)

11. Transition Metals Groups 3 – 12 They have many different properties
Less reactive than alkaline earth metals
Some are fairly non-reactive (Cu, Ag, Au)
Tungsten has the highest melting point
Mercury is a liquid with high density
Metals can be mixed together (alloy) to produce desirable properties.

12. F - Block Lanthanides (group 4f) Actinides (group 5f) #58 – 71#

13. Ions An ion is an atom that has lost or gained electrons.
Lose electrons – (+ ion)
Called cation
Gain electrons – (- ion)
Called anion

14. Ionization Energy The energy required to remove an electron.
If an electron is easy to remove, it takes little energy.
Period Trend
As you go from left to right across the period, it is harder to remove an electron – I.E. increases
Group Trend
As you go down a group, it is easier to remove an electron – I.E. decreases

15. Atomic Radius Size of an atom
Half the distance between 2 adjacent nuclei

16. Atomic Radius Period Trend Group Trend
As you go from left to right across a period, atomic radius decreases
Group Trend
As you go down a group, atomic radius increases.

17. Electron Affinity Energy change when an atom gains an electron.
Period Trend
As you go from left to right across a period, electron affinity increases.
Group Trend
As you go down a group, electron affinity decreases.

18. Electronegativity Ability to attract electrons Period Trend
0 – 4
Period Trend
As you go from left to right across a period, electronegativity increases.
Group Trend
As you go down a group, electronegativity decreases.