1. “The Periodic Table”

2. Organizing the Elements
Few elements (like Au and Cu), have been known for thousands of years - since ancient times
Only about 13 had been identified by the year 1700.
As more were discovered, chemists realized they needed a way to organize the elements.
Chemists used the properties of elements to sort them into groups (families).
Reactivity
Metal/Nonmetal
Physical appearance
Compounds they were found in

3. Mendeleev’s Periodic Table
Dmitri Mendeleev – a Russian chemist and teacher
Arranged elements in order of increasing atomic mass (the first “Periodic Table”)
_Left blanks_for yet undiscovered elements
When they were discovered, he had made good predictions
But, there were problems:
Ar and K; Te and I (mass didn’t increase)

4. A better arrangement
In 1913, Henry Moseley – British physicist, arranged elements according to increasing atomic number
This is the arrangement used today

6. The Periodic Law says:
When elements are arranged in order of increasing atomic number, there is a periodic repetition of their physical and chemical properties.
Horizontal rows = periods
There are 7 periods
Vertical column = group (or family)
There are 8 main groups identified by number & letter (IA, IIA, VIIA)

7. Areas of the periodic table
Three classes of elements are:
1) metals
2) nonmetals
3) metalloids
Metals: electrical conductors, have luster, ductile, malleable, found on the left hand side of the periodic table

9. Areas of the periodic table
Nonmetals: generally brittle and non- lustrous, poor conductors of heat and electricity
Some nonmetals are gases (O, N, Cl); some are brittle solids (S); one is a fuming dark red liquid (Br)

11. Metalloids on the Table
Metalloids: border the line-2 sides
Properties are intermediate between metals and nonmetals
Notice the heavy, stair-step line?
DRAW IT ON YOUR OWN TABLE

12. Metalloids on the Table

13. Squares in the Periodic Table
The periodic table displays the symbols and names of the elements, along with information about the structure of their atoms:

14. Groups of elements - Family names
Group IA – alkali metals
Forms a “base” (or alkali) when reacting with water (not just dissolved!)
Group 2A – alkaline earth metals
Also form bases with water; do not dissolve well, hence “earth metals”
Group 7A or 17 – halogens
Means “salt-forming”

15. Groups of Elements (Family Names)
Noble gases are the elements in Group 8A (also called Group18)
Previously called “inert gases” because they rarely take part in a reaction; very stable = don’t react

16. Groups of elements - Family names
Transition metals are in the “B” columns of the periodic table
Chemistry is more complex than the Main Group columns (“A” Groups)
A “transition” between the metal area and the nonmetal area
Examples are gold, copper, silver

17. #1. Atomic Size/ Number of Electron Shells
As we go down a group)
each atom has another electron shell,
so the atoms get bigger. Li Na K Rb

18. #2 - Atomic Number and Atomic Mass
The exceptions are Ar and K; Te and I
In these cases, the atomic mass of an element is greater than the one to the right of it.
As we go down a group or across a row the atomic number and atomic mass increases. (with a few exceptions)

19. #3 Types of elements
As you move from left to right on the periodic table, elements start as metals than transitions to metalloids and end on the right side as nonmetals.

20. #4 Reactivity
Elements in the center of the periodic table have low reactivity.
Reactivity increases as you move from the center to both the right and left side of the periodic table
On the left hand side, reactivity increases as you move down
On the right hand side, reactivity increases as you move up
The very last column on the right hand side (Noble Gases) is completely unreactive.

21. #5 - Chemical/Physical Properties
Elements in the same column on the periodic table have similar chemical properties (Reactivity, types of compounds formed, etc.)
Some columns even have similar physical properties
For example, Copper, Gold, and Silver are in a column.
All are malleable, ductile, good conductors and have a low level of reactivity
All are used in making coins and jewelry