1. History of the Periodic Table (Chapter 5. 1)
Johann Dobereiner
1817
Grouped elements into TRIADS, based on atomic mass & similar properties.
John Newlands
1863
Law of Octaves – when placed in order of increasing atomic mass, he found that similar properties appeared every 8 elements.
Dimitri Mendeleev
Lothar Meyer
(working separately)
1869
Placed elements in order of increasing atomic mass. Credited with creating 1st Periodic Table. Gave us “periodic law.”
Henry Moseley
1913
Arranged table in order of increasing atomic #, based on x-ray experiments. Gave us modern periodic law & table order.

2. Mendeleev’s Periodic Law
When elements are arranged by increasing atomic mass, there is a periodic repetition of chemical and physical properties

3. Moseley’s Periodic Law
When elements are placed in order of increasing atomic number, there is a periodic repetition of chemical and physical properties

4. The Periodic Table

5. The Periodic Table Arranged in increasing atomic number
Columns are called “groups” or “families”
Columns are numbered 1-18 (new way) or 1-8 with an “A” or “B” designation
“A” denotes MAIN GROUP, or REPRESENTATIVE, elements
“B” denotes TRANSITION elements

6. Classifying the Elements
Group 1 – Alkali Metals (except H)
Hydrogen is placed there for e- configuration purposes

7. Classifying the Elements
Group 2 – alkaline earth metals
Both Group 1 & 2 elements are very chemically reactive, reacting with air and water violently.
Group 1 is the most reactive

8. Classifying the Elements
Groups 3-12 (“B” elements) = transition metals and inner transition metals
Transition metals are in the main body of the table
Inner transition metals are the lanthanides & actinides

9. Classifying the Elements
Groups 13, 14 – a mix of metals & non metals, named for their top element
Group 13 Boron Group
Group 14 Carbon Group
Elements get more metallic as you go down the group

10. Classifying the Elements
Groups include non- metals (and some metalloids)
Mixed elements – more metallic as you go down groups; more non-metallic as you move across the periods

11. Classifying the Elements
Group 15 –Nitrogen group

12. Classifying the Elements
Group 16 – Chalcogens (oxygen group)

13. Classifying the Elements
Group Halogens

14. Classifying the Elements
Group 18 – Noble Gases
Non-reactive
Full valence shell of 8 e-
s & p sublevels full

15. Metalloids
A special group of 8 elements along the “stairstep” line on the periodic table
Have characteristics of both metals and non metals.
B, Si, Ge, As, Sb, Te, Po, At
Si and Ge are known as semiconductors – used in computers and other electronics

16. Metalloids