1. Arranging The Elements
Chapter 5 Section 1 pages

2. History 101- The Periodic Table
Dmitri Mendeleev – Russian Chemist – 1869
Discovered a pattern in the elements
His final arrangement – Arrange by increasing atomic mass
He left gaps in his table – for yet unknown elements to be discovered and placed.
He could predict the properties of the undiscovered elements by looking at the known elements that surrounded the gaps.

3. Our Current Periodic Table
Henry Mosely – British – 1914
Rearranged original table – CURRENT – by atomic number
This allowed all elements to fit the pattern

4. Classification of Elements on the Periodic Table
Type: Metal, Nonmetal and Metalloid
Number of outer electrons
Divided by the “zig-zag” line

5. Metals Metalloid Nonmetals Left of zig-zag line Few outer electrons
Most solid at room temperature
Metalloid
Border zig-zag line
~ half complete set of outer electrons
Nonmetals
Right of zig-zag line
May be full or almost full of outer electrons
More than half are gas at room temperature

6. Decoding the Elements of the Periodic Table
Atomic Number
= the number of protons/electrons
Symbol
1, 2, or 3 Letter Symbol – First letter is capitalized
Name
Sometimes named after people or places
Atomic Mass
Protons + Neutrons

7. Periods Side to Side – Horizontal (7)
Conductivity/Reactivity changes gradually as you move from left to right
Period Number = Number of energy Levels
1st Period = 1 Shell
2nd Period = 2 Shells
3rd Period = 3 Shells
4th Period = 4 Shells

8. Groups (Sometimes called Families)
Up and Down – Vertical (18)
Each group has similar physical and chemical properties
If you know the group number, you can determine the number of outer electrons.
Group 18 = 8 electrons
Group 1 = 1 electron
Except for He, it has 2 electrons
Group 2 = 2 electrons
The electrons in the outer shell are called “valence” electrons