The Periodic Table

1
The Periodic Table

• Origin
• Connection to Electron Structure

2
Why Do We Need a Periodic Table?

• By 1700, only 13 elements were known
• The rate of discovery increased in the 18th
  century
• But how could scientists make sense of all the
  elements?
• They needed a way to organize the elements

3
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

4
Lothar Meyer

• In 1864, Lothar Meyer published an early version
  of the periodic table, containing 28 elements
  classified into 6 families by their valence
  (combining power)
• 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.

5
Mendeleev

• In 1869, Dmitri Mendeleev proposed his periodic
  table
• There were 60 elements to organize
• He organized his elements by increasing atomic
  mass
• He left a space in his table if an element was
  unknown

6
Mendeleev

• Some people consider Meyer and Mendeleev the
  co-creators of the periodic table
• But 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.

7
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 dont easily react with other
elements.
8
Rows of the Periodic Table

• Rows of the PT are called periods.
• All of the elements in a period have their outer
  electrons in the same energy level.
• 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

9
The Four Regions of the PT
10
Four Kinds of Elements

• Metals
• Nonmetals
• Metalloids
• Noble gases

11
Metals

• The largest region of the PT 80

12
Non-metals

• The second largest region of the PT

13
Metalloids

• Have some properties of metals and some of
  nonmetals
• Silicon is useful in computers because they
  conduct electricity moderately
• Semi-conductors

14
Common Families

• Group 1 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 2 the Alkaline Earth Metals
• Group 7 the Halogens
• Literally means salt former

15
The Representative Elements

• These are the elements in Groups 1 7
• 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

16
Electron Configurations

• Elements in Groups have similar configurations
• Group 1
• Group 4

17
Valence electrons

• For any representative element, its group number
  indicates the number of valence electrons
  (outermost s and p electrons).

18
Transition Metals

• Elements in the block between the representative
  elements.
• These elements are filling their outermost d
  orbitals.
• Depending on the Table, groups in this block have
  different designations (1A vs 1, or 1B vs 1A)