1. The Periodic Table
An Introduction

2. I CAN describe the organization of the periodic table and draw a Lewis Electron Dot Structure for an element.

3. Development of the Periodic Table
By the 1800s, scientists starting looking for ways to organize the elements known at the time [about 68] into a meaningful arrangement.
A number of scientists developed tables of the elements. Since most had shortfalls, none of them were very good.

4. Mendeleev’s Table
In 1869, a RUSSIAN chemist by the name of DMITRI MENDELEEV made a successful table of the element [about 68 by this time].
Mendeleev made cards with all the known information about each element, including its atomic mass number.
He placed elements in horizontal rows from lowest to highest atomic mass number [amn].
When an element appeared that had similar properties to one already in a row, Mendeleev placed that element BELOW the previous one: this formed VERTICAL COLUMNS of elements.

5. Increasing ATOMIC MASS NUMBER

6. As Mendeleev continued placing elements into his table, sometimes he had to leave BLANK SPACES in order to keep all elements with similar properties in the same vertical column.
The blank spaces represented elements that were NOT YET DISCOVERED!!

7. He predicted where several other elements would fit.
Within his lifetime, 3 other elements were discovered that fit where he had predicted:
Scandium (Sc), Germanium (Ge) and Gallium (Ga)

8. Problems with Mendeleev’s Table
After Mendeleev died, more new elements were discovered that did not fit into his table as he had predicted.
Often, they were only off by a vertical column to the right or left of where he had predicted.
This problem was not solved for nearly two decades.

9. Moseley Rescues Mendeleev’s Table
A ENGLISH scientist named HENRY MOSELEY fixed the problems with Mendeleev’s table with a simple rearrangement.
By Moseley’s time (1913), it was possible to determine the atomic number of an element.

10. He rearranged the table by INCREASING ATOMIC NUMBER rather than by AMN.
When he did this…ALL the elements fit into the table!
The modern PT is still organized in this way!

11. The Concept of PERIODICITY
Mendeleev had discovered an important principle of chemistry:
PERIODICITY

12. Periodicity simply means that a property or characteristic REPEATS by a pattern.
In Mendeleev’s table, it turns out that the properties of the elements were repeated by every 8th element.

13. The Periodic Law
Mendeleev’s discovery lead to the proposal of the PERIODIC LAW.
The Periodic Law simply states that
“when the elements are arranged by increasing ATOMIC NUMBER, their physical and chemical properties repeat at regular intervals”.
This is where the name PERIODIC TABLE comes from!

14. Valence Electrons
The periodic table arrangement is based on the arrangement of electrons in an atom’s electron cloud.
The physical and chemical properties of an element are a result of the arrangement of electrons in the outermost energy level of the atom.

15. The outermost energy level is referred to as the VALENCE ENERGY LEVEL and the electrons in this outermost level are called VALENCE ELECTRONS, or Ve- for short!
The number of Ve- an atom has can easily be determined from the GROUP NUMBER THE ELEMENT IS IN on the periodic table.

16. Group 1 1 V e-
Group 2 2 V e-
Group 3-12 TRANSITION ELEMENTS [skip for now]
Group 13 3 Ve-
Group 14 4 Ve-
Group 15 5 Ve-
Group Ve-
Group 17 7 Ve-
Group 18 8 Ve-

17. Lewis Electron Dot Diagrams
Valence electrons [Ve-] are represented by Lewis Electron Dot Diagrams, or Lewis Structures for short.
A Lewis Structure consists of the element’s chemical symbol with dots (sometimes an x is used) placed around it to represent Ve-.

18. Writing a Lewis Structure
Find the element on the PT.
Go to the TOP of column to the group number and determine the number of Ve- the element has.
Write the element’s CHEMICAL SYMBOL.
Place DOTS (or Xs) around starting on the RIGHT SIDE and working COUNTERCLOCKWISE in a diamond pattern (side, top, side, bottom).

19. If you have MORE THAN 4 Ve-, make a second trip around, forming PAIRS OF Ve-.
There will NEVER BE MORE THAN 8 Ve-.
This is an atom’s MOST STABLE FORM and is known as an OCTET.

20. O Practice Problem Draw a Lewis Structure for Oxygen
1. Write the chemical symbol: O
2. Add dots to represent the Ve-
Oxygen is in column 16, so it has 6 Ve-

21. More Practice Problems
Draw a Lewis Structure for each of the following elements:
1. Calcium 2. Aluminum 3. Chlorine
4. Potassium 5. Carbon Sulfur
7. Boron 8. Xenon Magnesium
10. Nitrogen

22. Families of the Periodic Table

23. I CAN name and describe the families/groups and period/series of the periodic table.

24. Organization of the PT
Today, there are 18 VERTICAL COLUMNS of elements.
Each of these is called a FAMILY or GROUP.
all members have similar physical and chemical properties.
Each family has a FAMILY name.

25. There are 7 HORIZONTAL ROWS of elements.
These are called PERIODS or SERIES.
Each new period represents the additions of a new PRINCIPLE ENERGY LEVEL.
Generally not given names.

26. Instructions…do not write this as notes.
On your sample periodic table, number the left to right FAMILIES or GROUPS (1-18) and the up and down PERIODS or SERIES (1-7).

27. FAMILY or GROUP NUMBERS 
PERIOD or SERIES NUMBERS
FAMILY or GROUP NUMBERS  1 2 3 4 5 6 7

28. Instructions…do not write this as notes.
Begin labeling the NAMES of the FAMILES or GROUPS of the periodic table and write the short description of each on the BACK of the table.

30. Group 1 – Alkali Metals
The Alkali Metals are soft, silver colored metals that react strongly with water.
Stored under oil.
Not found free in nature…always part of a compound.

32. Group 2 - Alkaline Earth Metals
The Alkaline Earth Metals are series of silvery-gray metals that react with water, but not as violently as the alkali metals.

34. Groups 3-12 The Transition Metals
A variety of metal elements that have many uses. Form brightly colored compounds when they react with other elements.

35. Group 13 – Boron Family
The Boron Family is a group of metals with industrial uses in detergents (boron) and construction (aluminum).
Gallium metal will melt in your hand!

37. Group 14 – The Carbon Family
The Carbon Family has many important elements. Carbon is the basis of life. Silicon and Germanium are used in electronics, Tin and Lead in construction.

39. Group 15 – The Nitrogen Family
The Nitrogen Family contains both non-metals and metalloid elements.
Nitrogen makes up about 78% of air, Arsenic is used as a poison, Bismuth in in Pepto Bismol.

41. Group 16 – The Oxygen Family
Contains non-metals and metalloids.
Oxygen required for life. Sulfur is a main element in proteins. Polonium is radioactive.

43. Group 17 – The Halogen Family
The only group with gas, liquid and solid elements.
Name means “salt-forming”.
Chlorine is a disinfectant, fluorine is important for teeth, iodine is needed for proper thyroid function.

44. Halogen Family

45. Group 18 – The Noble Gas Family
All gases.
Don’t react with other elements normally.
All odorless and colorless.
Helium is a carrier, Neon is lights, Xenon insulates glass. Radon is radioactive and is the second leading cause of lung cancer.

46. Lanthanides
Actinides

48. The STAIR STEP (Zig-Zag) LINE roughly separated the METALS from the NON-METALS.

51. There are TWO LIQUID ELEMENTS:
MERCURY (metal) and BROMINE (non-metal)
There are 11 GAS ELEMENTS: All of Family 18 (Noble
Gases) along with FLUORINE and CHLORINE in
Family 17, and OXYGEN, NITROGEN and HYDROGEN.