THE PERIODIC TABLE
SCH3U1
Johann Wolfgang Dobereiner (1829)
• Dobereiner organized known elements into triads based
on their similar properties:
Li – Na – K
Ca – Sr – Ba
S – Se - Te
Cl –Br - I
John Newlands (1865)
• Ranked elements by atomic mass
• Noted that elements with similar properties occurred
every 8th element
• Newlands called this pattern The Law of Octaves
Dimitri Mendeleev (1869)
• Known as the father of the periodic table
• Assembled the first periodic table by atomic mass
• Elements with similar properties were placed in columns
• Left spaces for undiscovered elements and predicted their
properties
• The modern table is now arranged by increasing
atomic number
The Periodic Law
“ The properties of the elements recur in a systematic
pattern when the elements are arranged by atomic
number.”
Periods = horizontal rows
Groups (Families) = vertical columns
• contain elements with similar properties.
.
The Mendeleev Activity
1. Cut out and arrange the cards of the known elements
into a crude representation of the Periodic Table.
Hint: atomic mass always increases across a row and
down a column!
2. Show me your table and get the unknown elements
cards.
3. Place the unknown elements in the correct locations
and identify the elements.
4. Complete the Periodic Table Layout sheet and answer
the questions.
Mendeleev’s Predictions
• Mendeleev predicted the properties of the undiscovered
element ekasilicon (germanium) very accurately:
Property
Ekasilicon
(predicted 1869)
Germanium
(actual 1886)
Atomic mass
72
72.32
Colour
Dark grey
Greyish-white
Density (g/cm3)
5.5
5.47
Melting point (oC)
High
947
Formula of Oxide
EsO2
GeO2
Formula of Chloride
EsCl4
GeCl4
Organization of the Modern Periodic Table
Group Numbers
transition metals
inner transition metals
Alternate Periodic Tables:
Group 1: The Alkali Metals
Elements: Li, Na, K, Rb, Cs, Fr
Shared Physical Properties:
• Soft solids at room temp.
• Malleable
• Ductile
metallic
• Good conductors
of heat/electricity
character
Group 1: The Alkali Metals (continued)
Elements: Li, Na, K, Rb, Cs, Fr
Shared Chemical Properties:
• Form soluble bases (alkali solutions) in water
• Form oxides with formula X2O
Group 2: The Alkaline Earth Metals
Elements: Be, Mg, Ca, Sr, Ba, Ra
Shared Physical Properties:
• solids at r.t.
• Metallic character
•
Shared Chemical Properties:
• Form insoluble bases in water
• Form oxides with formula XO
Group 17: The Halogens
Elements: F, Cl, Br, I, At
Shared Physical Properties:
• Gas, liquid or solids at r.t.
• Non-metallic
Shared Chemical Properties:
• React with metals to form solid salts (MX)
• Form diatomic molecules (X2)
Group 18: The Noble Gases
Elements: He, Ne, Ar, Kr, Xe, Rn
Shared Physical Properties:
• Gases at r.t.
• Non-metallic
Shared Chemical Properties:
• Very unreactive
• Stable monoatomic atoms