1. The Ultimate Cheat-Sheet
The Periodic Table
The Ultimate Cheat-Sheet

2. Elementary My Dear Watson….
Elements are distinguished by the number of protons
Each element has unique properties
How are they arranged? Is there a pattern?

4. The “Original”

5. Why Do We Need a Periodic Table?
By 1700, only 13 elements were known
The rate of discovery increased in the 18th century (Davy, Lavoisier, Priestly)
But how could scientists know an element was “new?”
Chemists needed a way to organize the elements

6. How Was It Developed?
In 1829, Dobereiner published a classification system using triads
Triads are groups of 3 elements with similar properties
But, not all elements could be grouped into triads

7. Lothar Meyer
In 1864, Lothar Meyer published an early version of the periodic table
It contained 28 elements classified into 6 families by their valence (combining power)
This was the first time that elements had been grouped and ordered according to their valence.
Work on organizing the elements by atomic weight had hitherto been stymied by inaccurate measurements of the atomic weights.

8. de Chancourtois One of the first to notice periodicity
In 1862 developed a cylindrical design
Ignored due to “geological terms”

9. How Was It Developed….
In 1865, Newlands classified elements into 11 groups
Noticed that many groups differed by “8”
He called this his “Law of Octaves”

10. Development Other systems were explored…
In 1869, Dmitri Mendeleev proposed his periodic table
He played “chemical solitaire” on the train
There were 60 elements to organize

12. How Did Mendeleev Do It?
He organized the elements by increasing atomic mass and “combining power”
He left a space in his table if an element was unknown
In time, those spaces were filled in with elements that matched his predictions

13. Elements’ Properties are Predicted
Property
Mendeleev’s Predictions in 1871
Observed Properties
Molar Mass
Oxide formula
Density of oxide
Solubility of oxide
Scandium (Discovered in 1877)
44 g
M2O3
3.5 g / ml
Dissolves in acids
43.7 g
Sc2O3
3.86 g / ml
Molar mass
Density of metal
Melting temperature
Gallium (Discovered in 1875)
68 g
6.0 g / ml
Low
Dissolves in ammonia solution
69.4 g
5.96 g / ml
30 0C
Ga2O3
Dissolves in ammonia
Color of metal
Chloride formula
Density of chloride
Boiling temperature
of chloride
Germanium (Discovered in 1886)
72 g
5.5 g / ml
Dark gray
High
MO2
4.7 g / ml
MCl4
1.9 g / ml
Below 100 oC
71.9 g
5.47 g / ml
Grayish, white
900 0C
GeO2
4.70 g / ml
GeCl4
1.89 g / ml
86 0C
Fitting in New Elements
“The crowning achievement of Mendeleyev’s periodic table lay in his prophecy of new elements. Gallium, germanium, and scandium were unknown in 1871, but Mendeleyev left spaces for them and even predicted what the atomic masses and other chemical properties would be. The first of these to be discovered in 1875, was gallium. All the characteristics fitted those he had predicted for the elements Mendeleyev called eka-aluminum – because it came below aluminum in his table.”
-Eyewitness Science “Chemistry” , Dr. Ann Newmark, DK Publishing, Inc., 1993, pg 23
In the 1860’s, Mendeleev and the German chemist Lothar Meyer, each working alone, made an eight-column table of the elements.
However, Mendeleev had to leave some blank spots in order to group all the elements with similar properties in the same column. To explain these blank spots, Mendeleev suggested there must be other elements that had not yet been discovered. On the basis of his arrangement, Mendeleev predicted the properties and atomic masses of several elements that were unknown at the time.
Mendeleev left blanks in his table for undiscovered elements.
Mendeleev predicted properties and masses of unknown elements correctly.
O’Connor Davis, MacNab, McClellan, CHEMISTRY Experiments and Principles 1982, page 119,

14. Mendeleev
Some people consider Meyer and Mendeleev the co-creators of the periodic table
Most agree that Mendeleev's accurate prediction of the qualities of what he called eka-silicon (germanium), eka-aluminium (gallium) and eka-boron (scandium) qualifies him for deserving the majority of the credit for studies

15. Mendeleev did not know the structure of atoms and that the number of protons was unique for each element
Now the periodic table is arranged by increasing atomic number

16. The Modern Periodic Table
Is an organized display of elements
Is arranged so that elements with similar properties fall into the same group
Is used to predict the behavior of elements
The “Noble Gases” don’t easily react with other elements.

17. Rows of the Periodic Table
Rows of the PT are called “periods.”
All of the elements in a period have the same number of energy levels for their valence (s & p) electrons

18. K and Kr are very different
Periods (cont.)
Elements close to each other in the same period are more similar than those further away.
K and Ca are similar
K and Kr are very different

19. So…
Properties of the elements within a period change as we move across a period from left to right
The pattern of properties within a period repeats as we move from one period to the next

20. The Periodic Law
When elements are arranged in order of increasing atomic number, there is a periodic repetition of their physical and chemical properties

22. Regions of the PT

23. 1) Metals
The largest region of the PT ~ 80%

24. Properties of Metals Excellent conductors of heat and electricity
Usually lustrous, ductile, and malleable.
Gold charm
Sodium metal
Copper wire

25. 2) Nonmetals
The second largest region of the PT

26. Properties of Nonmetals
Poor conductors of heat and electricity
Most are gases or brittle solids at room temperature.
Chlorine gas
Graphite
Diamond

27. 3) Metalloids Have some properties of metals and some of nonmetals
Silicon is useful in computers because they conduct electricity “moderately”
Semi-conductors

28. Other Uses of Metalloids
Lasers
Infrared sensors
Alloys
Glass products
Added Impurities

29. The Elements at the Bottom
These are the lanthanides and actinides
Glenn Seaborg “moved” these

30. Special Groups of Elements
Group 1A – the Alkali Metals
The name alkali comes from the Arabic al aqali, meaning “the ashes.”
Wood ashes are rich in compounds containing sodium and potassium
Group 2A – the Alkaline Earth Metals
Group 7A – the Halogens
Literally means “salt former”

31. The Representative Elements
These are the elements in Groups 1A – 7A
They represent a wide range of properties
Metals, nonmetals, and metalloids
Solids, liquid (Br), and gases
The highest level s & p orbitals are NOT filled

32. Examples Electron configurations for Group 1A

33. Group Number and e- Number
For any representative element, its group number equals the number of electrons in the highest occupied energy level (valence electrons).
Group 1A
Group 4A

34. Noble Gases NOT considered representative elements Unreactive Uses:
Krypton is mixed with Argon in fluorescent lights (also to render Superman inert)
Neon is used for signs
Helium is used in weather and toy balloons

35. What About The “Ones in the Middle”
These have different letter designations, depending on the table
These are also called
Transition metals
Inner transition metals

36. Transition Metals
The highest occupied s sublevel and a nearby d sublevel contain electrons
These elements are also called d -block elements

37. The Inner Transition Metals
AKA: the lanthanides and actinides.
The highest occupied s sublevel and a nearby f sublevel generally contain electrons.

38. f-orbitals

39. Blocks of Elements

40. Rare Earth Elements
Scandium, Yttrium, Lanthanum, and Cerium through Lutetium
Used in electronics
Thulium (Tm) – lasers & x-rays
Neodymium (Nd) - magnets
Not rare – hard to separate
Elements very similar
Charges are 3+

41. The Racetrack Design