1. THE PERIODIC TABLE

2. Dmitri Mendeleev
A Russian scientist who began to classify the 60 known elements of his time
Worked with the indivisible model of an atom
Atomic masses were known in comparison to hydrogen, which was set as "1"
Mendeleev was the youngest of 14 or 17 kids born into a well-educated and prosperous Siberian family, they lost their posessions in a fire, his father went blind and reduced to poverty, his mom hitchhiked miles to St.Petersburg (like going from London to Equatorial Guinea) and put him in school and promptly died.

3. “I began to look about and write down the elements with their atomic weights and typical properties, analogous elements and like atomic weights on separate cards, and this soon convinced me that the properties of elements are in periodic dependence upon their atomic weights.” --Mendeleev, Principles of Chemistry, 1905, Vol. II

4. Mendeleev discovered that the properties of the elements repeated at regular intervals when the elements are arranged in order of increasing atomic mass
periodicity: the occurrence of similar physical and chemical properties of elements at regular intervals

5. He left blank spaces for where he predicted (based on properties) an element should be
He predicted (accurately!) the properties of yet-undiscovered elements!!!

7. Observed properties of Eka-Silicon and observed properties of Germanium:
Property
Observed for Si
Predicted for Eka-Silicon
Observed for Sn
Found for Ge
Atomic Mass
Melting Point (oC)
Density (g/cm3)
Boiling point of chloride
(oC) 28
1410
2.33
57.6 72
High
5.5
100
118
232
7.28
114 73
947
5.35 84

8. In the meantime…
Thomson and Rutherford discovered the proton and the electron

9. Chadwick, in Rutherford’s lab made another discovery: the neutron!

10. SO… an atom is made of
Positive protons, mass of 1, symbol p+
Uncharged neutrons, mass of 1, symbol no
Negative electrons, mass of 0, symbol e-

11. Atomic mass = number of protons + neutrons
Atomic number = number of protons
Number of protons = number of electrons (in a neutral atom)

12. Moseley working together with Rutherford discovered that the element's properties could be even better predicted using the number of charges the atom had: atomic number

13. elements were re-arranged by atomic number (as in the modern Periodic Table)
elements arranged in order of increasing atomic number show a periodic repetition of properties
each column of the periodic table (called a group) has similar properties (periodic trends)
The vertical columns are called "groups“ or “families”.
The horizontal rows are called "periods".
The Periodic Law
- chemical and physical properties of element vary in a periodic way with their atomic number

14. The modern Periodic Table
Scientists divide elements into 3 categories
1. Metals
Alkali metals
Alkaline earth metals
Transition elements
Inner transition elements
2. Non-metals
Halogens
Noble gases
3. Metalloids

18. representative elements
transition elements
inner transition elements

19. alkali metals
noble gases
alkaline earth metals
halogens
transition metals
lanthanoids
actinoids

20. Metals left side and centre of periodic table
Solid at room T (except mercury, Hg)
Silver (except Cu and Au)
Shiny, conduct electricity and
heat, malleable and ductile

21. malleable:
capable of being shaped, the degree to which it can be shaped by pounding with a hammer
ductile:
physical property of being capable of sustaining large deformations without breaking (for example being drawn into a wire)

22. Non-metals Right side of periodic table Found in all three states
Variety of colours
Poor conductors of heat/electricity
Usually brittle (having little elasticity: easily cracked or fractured or snapped )

23. Metalloids Along zig-zag line dividing metals and non-metals
Metalloids are: Boron, Silicon, Germanium, Arsenic, Antimony, Tellurium, Polonium
Have some metallic and non-metallic properties
Ex. Si - silicon: shiny, nonmalleable, a semi-conductor