1. The Periodic Table

2. What is the Periodic Table?
The periodic table is a chart that chemists to organize elements based on their properties
The properties that are used to organize elements are:
-- atomic number
-- number of valence electrons
-- energy level of the valence electrons

3. Putting Together the Periodic Table
In the 1800’s, many scientists suggested putting the 55 known elements (at the time) into a chart based on atomic mass, however, no chart was able to make sense. . .
In the 1860’s, a Russian scientists named Dimitri Mendeleev started looking at other properties of the elements:
-- he looked at the reactivity of metals, for example how certain metals tarnish in air
-- he looked at how certain gases are irritating if you breath them in
Mendeleev made cards listing the properties of each element and began to organize his chart

4. Mendeleev’s Chart
Mendeleev managed to put two important characteristics of each element on his cards:
-- atomic mass
-- number of bonds each element formed
From his cards, Mendeleev organized a chart in order of increasing mass
-- he also put his elements in different groups based on the way they bonded to other elements
This turned into the skeleton of today’s periodic table
-- Mendeleev’s table was so good, he was actually able to predict the atomic mass of three undiscovered elements!

5. The Modern Table
The modern periodic table came into development in the early 1900’s with the discovery of atomic number. . .
From this, we have the modern table, where the elements increase from left to right by atomic number and are placed in columns based on similar physical properties and bonding patterns

6. Metals and Non-Metals
On the modern table, the elements on the left of the table (except hydrogen) are all metals and have metallic properties
On the right side of the table, all the elements are non-metals
Between the metals and non-metals is a “staircase” of elements called metalloids (semi-metals)
-- these elements have some metallic and some non- metallic properties
-- the metalloids are: Boron, Silicon, Germanium, Arsenic, Antimony, Tellurium, and Astatine

7. Image of Metals and Nonmetals on the Periodic Table

8. Reading Squares on the Table
Each element has its own square on the periodic table which tells you several important things about the element:

9. Periods and Groups
The rows on the periodic table are called periods, and are numbered 1 – 7 from top to bottom
-- elements increase in atomic number from left to right in a period
-- the elements in a period have very different chemical properties, and range from metals to nonmetals
The columns on the periodic table are called groups or families, and are numbered 1 – 18
-- each element in a group has similar properties
-- if you don’t use the transition metals, the groups can be renumbered I – VIII, which will be important later

10. The Secret of the Table
The secret of the table is that it allows you to predict the properties of an element (specifically, the electrons of an element) based on the periods and groups. . .
For example, lets draw a Bohr model of carbon (atomic # 6)
How many valence electrons does carbon have?
In what group (Roman Numeral) is carbon?
In what energy level are these valence electrons?
In what period is carbon?

11. The Secret of the Table
The group (I – VIII) of an element tells you how many valence electrons the element has. . .
The period (1 – 7) of an element tells you what energy level those electrons are in. . .
THIS DOES NOT WORK FOR TRANSITION METALS!!!
-- if you need to know the valence electrons of transition metals, I will tell you. . .