1. The Periodic Table

2. History of the Periodic Table
Dmitri Mendeleev organized the 63 known elements in 1860
Based on increasing atomic mass and arranged in columns based on properties and reactivity
Left gaps where he predicted undiscovered elements

3. Mendeleev’s prediction “Ekasilicon” (1872):
Actual properties of Germanium (discovered in 1886)
Atomic mass: 72
High melting point
Density = 5.5 g/cm3
Dark gray metal
Density when combined with oxygen: 4.7 g/cm3
Atomic mass: 72.61
Melting point: 938°C
Density = g/cm3
Gray metal
Density when combined with oxygen: 4.23 g/cm3

4. Lanthanide and Actinide Series
Horizontal rows are called periods
“periodical” – repeating in a pattern
Vertical columns are called groups or families
Similar chemical properties
Lanthanide and Actinide Series

5. Metals Properties of metals include: Solid at room temperature
Malleable
Ductile (can be drawn into wires)
Good conductors of heat and electricity

6. Nonmetals Properties of nonmetals include:
Mostly gases at room temperature
Brittle
Poor conductors of heat and electricity at room temperature
Poor conductors are called insulators

7. Metalloids
Metalloids have some metallic and some nonmetallic properties
Some metalloids can be semi-conductors
Under some conditions they are good conductors, and under other conditions they are insulators

8. Trend #1: Atomic Mass
In general, atomic mass increases across a period

9. Trend #2: Atomic Radius
Atomic radius generally decreases across a period
More protons = stronger grip on the electrons in the energy level
Atomic radius generally increases down a group
This is because with each new group, a new S-orbital (new energy level) is added

10. Atomic Radius in the periodic table

11. Trend #3: Reactivity
Elements in the same group generally have the same reactive properties
This is because elements in the same group have the same number of valence electrons
Valence electrons are the electrons in an atom’s outermost orbital

12. Alkali Metals Group 1 (minus hydrogen) Oxidation number +1
Highly reactive
Tend to react with group 17 (or 7A) elements

13. Tends to react with group 16 (or 6A)
Alkaline Earth Metals
Group 2
Oxidation number +2
Very reactive
Tends to react with group 16 (or 6A)

14. Halogens Elements in group 17 (or 7A) are called halogens
7 valence electrons
Oxidation number -1
nonmetals
They often react with the alkali metals

15. They have a full outer shell 2 for He 8 for the others Non-reactive
Noble Gases
Group 18 (8A)
Oxidation number 0
They have a full outer shell
2 for He
8 for the others
Non-reactive