Section 2 Tour of the Periodic Table p. 111 Chapter 4 Section 2 Tour of the Periodic Table p. 111

Understand the arrangement of the periodic table Objectives Understand the arrangement of the periodic table Predict the properties of unknown elements

I. Organization of the Periodic Table Mendeleev- first to arrange elements into a table Periodic Law- similarities in properties occur in regular patterns Arranged according to atomic number A. Helps to determine electron configuration (p. 114) Horizontal rows, called periods, tell number of electron shells B. Elements in the same group have similar properties Vertical columns are called groups and tell the number of valence electrons

Atomic Number (Z) Symbol Atomic Mass (A) Electron Configuration

YouTube - The Elements Animation

II. Some atoms form ions- charged particle A. Cations- positive ions B. Anions- negative III. Structure of Atoms differ A. Atomic number (Z number)- number of protons in an element U is the largest natural occurring element (Z=92) B. Atomic mass (A number)- Total number of protons and average number of neutrons 1. It is a weighted average that gives more common isotopes more effect on the # 2. Atomic Mass Unit (AMU) – 1/12 mass of a carbon atom