Aim: How are Elements Organized in the Periodic Table? DO Now: 1. How would you organize these buttons? 2. How do you think elements are organized in the periodic table? 3. Write at least one trend you notice about the elements in the periodic table.

History of the Periodic Table The first periodic table was developed by chemist Dmitri Mendeleev; arranged elements in order of increasing atomic mass. (look at Te and I; not in order of increasing mass) The modern periodic law states: elements arranged in order of increasing atomic numbers. Elements are sorted into groups based on similar properties.

Periods and Groups Periods Groups or Families Vertical columns Horizontal rows The # of the period indicates the # of energy levels (shells) in the element The # of valence electrons (electrons in outer shell) increases from left to right Properties of elements change across a period Vertical columns Most elements within the same group have the same number of valence electrons (electrons in outermost shell); therefore, have similar chemical properties

Three Classes of Elements 1.Metals Alkali Metals Alkaline Earth Metals Transition Metals Inner Transition Metals 2.Metalloids 3.Nonmetals Halogen Noble Gases

Metals vs Non Metals Properties Metals solids at room temperature are malleable are ductile have luster good conductors of heat and electricity Properties of Nonmetals many are gases at room temperature not malleable, tend to be brittle in the solid phase. surface is dull poor conductors of heat and electricity

Metalloids an element (e.g., germanium or silicon) whose properties are intermediate between those of metals and solid nonmetals