This document describes how elements are classified and organized on the periodic table. It defines metals, nonmetals, and metalloids, and explains their characteristic properties. Metals are shiny, solid conductors that are malleable and ductile, while nonmetals exhibit varying states, are dull, and are poor conductors. Metalloids have some properties of both. Elements are arranged vertically in groups with the same number of valence electrons and horizontally in periods with the same number of electron shells. The periodic law states that properties repeat periodically with increasing atomic number.

1. Classification of Elements January 15, 2010

2. Objectives Describe characteristics of metals, nonmetals, and metalloids Define period, periodic law, family, malleable, ductile. valence electrons Describe how elements are arranged on the periodic table

4. Henry Mosley (1914) Determined that each atom has a unique number of positive charges. Discovered isotopes Rearranged Mendeleyev’s table by their atomic number

6. Periodic Law Because properties of elements repeated in an orderly way, it was called periodic . Properties of elements are a function of their atomic numbers.

7. Metals shiny (they have luster) solids at room temperature good conductors malleable - capable of being hammered out into thin sheets ductile - drawn out into wire or threads

8. Located to the left of the zigzag line Most elements are metals Usually have few valence electrons

9. Non-metals Can be found as solids, liquids, or gases at room temperature Typically dull and brittle Poor conductors All non-metals except hydrogen are found on the right side of the zigzag line Many valance electrons

10. Metalloids Border both sides of the zigzag line each has some of the properties of a metal and non metal can become good conductors under certain conditions such as high temperatures Also called semiconductors

11. Elements are arranged: Vertically into Groups or Families Horizontally Into Periods

12. Every element in a family has the same number of valence electrons

13. Definition of Valence Electrons Valence electrons Number of electrons an element has in its outermost orbital Periodic Table shows this by classifying the elements in families that all have the same number of valence electrons Group number tells how many valence electrons each element in that family will have

14. The group 2 atoms all have 2 electrons in their outer shells Be (Beryllium) Atom Mg (Magnesium) Atom

15. If you looked at an atom from each element in a period Each atom has the same number of electron shells .

16. The period 4 atoms each have 4 electron containing shells K (Potassium) Atom Fe (Iron) Atom Kr (Krypton) Atom 4 th Shell