4. The Periodic Table Cl 35.5 Br 79.9 I 126.9
History of the Periodic Table
J.W. Dobereiner – elemental triads
Elements in a triad have similar properties
The properties of the middle element are ~ averages of the others
Element
Atomic
Mass Cl
35.5 Br
79.9 I
126.9

6. The Periodic Table J.A.R. Newlands – Law of Octaves
Arranging elements by increasing atomic mass results in every 8th element having similar properties
Demonstrated that there is a pattern to elemental properties

7. The Periodic Table Dmitri Mendeleev
Arranged elements in order of increasing atomic mass and made a table
Switched the order of some elemental pairs to make them fit

8. Mendeleev’s Periodic Table

9. Comparison of Ekasilicon and Germanium
The Periodic Table
Mendeleev predicted the properties of undiscovered elements:
Comparison of Ekasilicon and Germanium
Property
Ekasilicon
Germanium
Atomic Mass (amu) 72
72.59
Density (g/mL)
5.5
5.35
Melting Pt. (oC)
High
947
Color
Gray

10. The Periodic Table Henry Moseley –
discovered that the correct way to arrange the elements is in increasing order of atomic number

11. Periodic Law
When elements are arranged in order of increasing atomic number, their physical and chemical properties show a periodic pattern

12. Group - vertical columns (1-18)

13. Period – horizontal row (1-7)

14. Family Names Groups 1-2; 13-18 – Representative Elements
Group 1 - Alkali Metals
Group 2 – Alkaline Earth Metals
Group 3 to 12 – Transition Metals
Group 13 – Boron Family

15. Family Names Group 14 – Carbon Family Group 15 – Nitrogen Family
Group 16 – Chalcogens
Group 17 – Halogens
Group 18 – Noble (Inert) Gases

24. Periodic Table
The lanthanoid and actinoid series are known as the InnerTransition Metals
Hydrogen – not really a member of any group – definitely a nonmetal in physical properties but has certain chemical properties similar to the group 1 elements

25. Metals, Nonmetals, and Semimetals
Shiny luster
Conduct electricity
Conduct heat
Usually solid at room temperature
Malleable
Ductile
Gold Nugget

26. Metals, Nonmetals, and Semimetals
Dull luster
Poor electrical conductor
Poor conductor of heat
Many are gases at room temperature
Brittle
Sulfur

27. Metals, Nonmetals, and Semimetals
Semimetals (metalloids)
Properties of both metals and nonmetals
Semiconductors
B, Si, Ge, As, Sb, Te, At
Silicon

28. Periodic Trends
Periodic Trends – predictable changes in the properties of the elements as you move through the periodic table

29. Periodic Trends
Atomic Radius – the distance from the center of an atom to its outermost electron
Atoms become larger as you go down a given group
Atoms become smaller as you go from left to right in a given period

33. Periodic Trends Ionic size
Ions increase in size as you go down a given group
Metal and nonmetal ions decrease in size as you go from left to right in a given period