1. Chapter 5
The Periodic Table

2. Mendeleev’s Periodic Table
His strategy for organizing the elements was modeled on a card game.
Key Point: Mendeleev arranged the elements into rows in order of increasing mass so that elements with similar properties were in the same column.
Within a column mass increases from top to bottom

3. Why did Mendeleev leave spaces?
A periodic table is an arrangement of elements in columns based on a set of properties that repeat from row to row.
Why did Mendeleev leave spaces?
Because many elements had not been discovered.
Key Point: The close match between Mendeleev’s predictions of new elements showed how useful his periodic table could be.

4. The Periodic Law
Key Point: Properties of elements repeat in a predictable way when atomic numbers are used to arrange elements into groups.

5. Periodic Law Periods Groups Each row is a period Runs
Number of elements per row varies
Energy level = row
As you move left to right, atomic # increases
Groups
Each column
Runs
Elements within a group have similar properties
Ex. Na and K

6. Periodic law: the pattern of repeating properties
4 pieces of information shown in Fig. 7
Atomic number
Element Symbol
Element Name
Atomic Mass
Atomic Mass: is a value that depends on the distribution of elements isotopes and the masses of those isotopes.

7. Classes of Elements Metals
The majority of elements on the periodic table
Good conductors of electric current and heat
Most are solids at room temperature
Malleable and ductile
Left side of dark line

8. Nonmetals Poor conductors of heat and electric current
Low boiling points
Gases at room temperature
Tend to be brittle
Extremely reactive
Right side of dark line

9. Metalloids
Properties fall between metals and nonmetals
On the dark line completely
Across a period from left to right the elements become less metallic and more nonmetallic in their properties.

10. 5.3 Groups
Valence electrons: is an electron that is in the highest occupied energy level of an atom. It is equal to their group number!
These electrons play a role in chemical reactions.
Key Point: Elements in a group have similar properties because they have the same number of valence electrons.

11. Alkali Metal Alkaline Earth Metals Group 1A A single valence electron
Very Reactive
Alkaline Earth Metals
Group 2A
2 valence electrons
Harder and higher melting point than 1A

12. Boron Family Carbon Family Nitrogen Family Group 3A
3 valence electrons
Al is the most abundant in the Earth’s crust
Carbon Family
Group 4A
4 valence electrons
1 nonmetal, 2 metalloids, 2 nonmetals
Nitrogen Family
Group 5A
5 valence electrons
2 nonmetals, 2 metalloids, 1 metal

13. Halogens Noble Gases Group 7A 7 valence electrons
A range of physical properties
Noble Gases
Group 8A
All but He, have 8 valence electrons, He has 2 valence electrons
Colorless, odorless and extremely unreactive

15. Tell the number of valence electrons for the following:Na F I Al C Pb Ba