1. Chapter 17
Section: 3

3. In the late 1800s, Dmitri Mendeleeve, a Russian chemist, searched for a way to organize the elements.
He discovered that they followed a pattern and soon organized the periodic chart or period table.
When creating the chart Mendeleeve soon realized to keep everything lined up he would have to leave blank spots.

4. By studying the chart with the blank areas he was able to successfully predict what the properties of the unknown elements were.
Modern science has tweaked the chart created by Mendeleeve. He arranged the chart in order of atomic mass. This led to a few issues of the chart no flowing well. Moseley , an English scientist, discovered if you arranged it by atomic number it all worked nicely.

5. Arrangement of the periodic table
Groups– the vertical columns in the table
There are 18 groups or families
Groups are arranged because they all have something in common.
If you look at group eleven: copper, silver, and gold are all similar.
Periods—horizontal rows in the table
Arranged by the atomic number
Increase by one proton and one electron as you go to the right
There are three main categories in the table: metals, nonmetals, and metalloids

6. Electron Cloud Structure
In a neutral atom electrons equal the number of protons.
Electrons have different amounts of energy.
To illustrate this they place them in different levels.
Electrons fill these levels from the inside out.
Elements in the same group have the same number of electrons in their outer energy level

8. Energy levels of an electron cloud
There are 7 energy levels.
Energy level one can contain a maximum of two electrons
Level two can contain a maximum of eight electrons
A complete and stable outer energy level will contain eight electrons

9. There are seven periods just like there are seven energy levels.
Each period tells you what energy level you will find an electron in.

10. Electron dot diagram
An electron dot diagram uses the symbol of the element and dots to represent the electrons in the outer energy level.

11. Groups have similar properties.
A common property of halogens (group 17) is they readily react with group 1 elements.
Why do you think this is?
Not all groups will combine easily. Group 18 are relatively unreactive.

12. Element in the universe
Scientists have studied the elements enough that they believe hydrogen and helium are the two main building blocks for all other elements.
Inside stars hydrogen is pushed to gather to from helium, then a helium and hydrogen are pushed together to from lithium , etc.
Many believe that supernovas are what spread the elements throughout the universe.

13. Summary
Mendeleeve organized the elements using increasing atomic mass and chemical and physical properties
He left blank spaces in his table to allow for elements that were yet undiscovered.
Moseley correct the problems in the periodic table by arranging the elements in order of increasing atomic number.

14. The vertical columns in the periodic table are known as groups
The vertical columns in the periodic table are known as groups. Elements in a group have similar properties
Electrons within the electron cloud have different energy levels.
The period table is divided into these regions: Periods, metals, nonmetals, and metalloids.
Scientist around the world are continuing to try to synthesize new elements.