The document describes the classification of elements on the periodic table. Elements are arranged vertically into groups based on their valence electrons and horizontally into periods based on their atomic number. Metals are generally found on the left side of the periodic table, are shiny, good conductors, malleable, and ductile. Nonmetals are generally found on the right side, can exist as solids, liquids or gases, are typically dull and brittle, and poor conductors. Metalloids border both sides and have properties of both metals and nonmetals.

1. Classification of Elements January 13, 2011

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

8. Valence Electrons Number of electrons an element has in its outermost orbital Families have the same number of valence electrons Group number tells how many valence electrons each family will have

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

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

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

12. 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

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

14. 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

15. 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