1. The Periodic Table
SCH3U1

2. 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

3. 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

4. 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

5. The modern table is now arranged by increasing atomic number

6. 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. .

7. The Mendeleev Activity
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!
Show me your table and get the unknown elements cards.
Place the unknown elements in the correct locations and identify the elements.
Complete the Periodic Table Layout sheet and answer the questions.

8. 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

9. Organization of the Modern Periodic Table
G r o u p N u m b e r s
noble gases
halogens
P e r I od N u m b e r s
alkali metals
metalloids
alkaline earth metals
transition metals
inner transition metals

10. Alternate Periodic Tables:

11. Group 1: The Alkali Metals
Elements: Li, Na, K, Rb, Cs, Fr
Shared Physical Properties:
Soft solids at room temp.
Malleable
Ductile
Good conductors of heat/electricity
metallic character

12. 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

13. 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

14. 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)

15. 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