1. Periodic Table Development
Chapter 6.1
Periodic Table Development

2. 1790’s Lavoisier makes a list of all known elements (23)
First compilation of elemental information

3. 1800’s
Discovery and use of electricity allows scientists to use electrolysis to decompose compounds
Spectrometer invented
Enables new elements to be identified
Triples the number of known elements
Knowledge of properties also increases and is standardized

4. 1817 - Dobereiner Grouped elements in triads
Mass of the middle element was the average of the other two

5. 1864 - Newlands Arranged elements by increasing atomic mass
Developed “Law of Octaves”
Properties repeated every 8 elements
Similar to notes on a piano
7 groups of 7 elements

6. 1864 - Newlands Not a bad first attempt, but a lot of flaws
Law of octaves did not work for all elements
Other scientists resented the use of the word octaves as unscientific

7. 1869 - Mendeleev Arranged elements by increasing atomic mass
Put elements with similar properties in the same column
Expanded Newland’s table after n=2
Put spaces for 17 elements in n=3&4
Left blank spaces and predicted properties for undiscovered elements

8. 1869 - Mendeleev Flaw in Mendeleev’s table
As atomic masses became more accurate, more elements seemed to be misplaced

9. 1913 - Moseley Discovered the proton and atomic number
Arranging elements by atomic number corrected the flaws of both Newland and Mendeleev
Periodic Law – Properties of elements are periodic functions of their atomic numbers

10. Modern Periodic Table Periods – horizontal rows
Groups/Families – vertical columns
Similarities within a group
Electron configurations
Electron dot diagrams
Reactivity of elements
Group 18 (noble gases) only group with full outer energy levels and composed solely of non-metals

11. Classifying the Elements

12. Metals Left side of the periodic table Properties Hard Lustrous
good conductors
Malleable
Ductile

13. Metals 3 or fewer electrons in their outer energy level
Reactivity increases as you move down and left across the periodic table

14. Metals Group 1 – Alkali Metals Group 2 – Alkaline Earth Metals
1 electron in outer level
Most reactive of all metals
Group 2 – Alkaline Earth Metals
2 electrons in outer level
Highly reactive

15. Transition Metals – Groups 3-12
1 or 2 electrons in outer level
Contain numerous exceptions to the ground state electron configurations
Elements with a full or partially filled sub-level are slightly more stable
Properties of elements in groups are still similar
Group 11 – coinage metals

16. Transition Metals – Groups 3-12
Often provide the color in gemstones when the transition element is substituted into a crystal
Corundum (Al2O3)
Cr replaces some Al producing Rubies
Fe replacing Al for Topaz
Ti replacing Al for Sapphire
Beryl (Be3Al2Si6O18)
Cr replaces Al to produce Emeralds
Substitution occurs because the atoms have similar atomic radii and valence electrons

17. Inner Transition Metals
Lanthanides & Actinides
Small differences in electron configurations
All elements in the family could be placed in one block of the periodic table
Used as phosphors
Emit light when hit with electrons
Examples – TV's computer monitors

18. Non-Metals Right side of periodic table
5 or more electrons in their outer level
Gases or brittle solids at room temperature
More reactive as you move up and to the right on the periodic table

19. Non-Metals Group 16 (6 electrons) Group 17 (7 electrons)
Chalcogens
Group 17 (7 electrons)
Halogens (salt former)
Highly reactive
Group 18 (8 electrons)
Noble Gases
Extremely unreactive

20. Metalloids Elements separating the metals from the non-metals
Properties of both metals and nonmetals
Properties get more metallic as you move down the group