1 Chapter 3 Electronic Structure and the Periodic Law 3.1 The Periodic Law and Table Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings

2 Periodic Law Scientist looked for order in detailed studies of elements and had produced an abundance of chemical information. Scientist looked for a systematic approach to studying chemistry. Two scientist, made the same important contribution independently and simultaneously named Julius Meyer and Dmitri Mendeleev. Both schemes were based on the Periodic Law.

3 Definition of the Periodic Law The periodic law is a statement about the behavior of the elements when they are arranged in a specific order. In its present form, it is stated as follows: Elements with similar chemical properties occur at regular (periodic) intervals when the elements are arranged in order of increasing atomic numbers.

4 Groups and Periods On the periodic table, elements are arranged according to similar properties. groups contain elements with similar properties in vertical columns. periods are horizontal rows of elements.

5 Groups and Periods Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings

6 Periodic Table by Meyer and Mendeleev Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings

7 Group Numbers use the letter A for the representative elements (1A to 8A) and the letter B for the transition elements. also use numbers 1-18 to the columns from left to right.

8 Names of Some Representative Elements Several groups of representative elements are known by common names. Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings

9 Alkali Metals Group 1A(1), the alkali metals, includes lithium, sodium, and potassium. Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings

10 Halogens Group 7A(17) the halogens, includes chlorine, bromine, and iodine. Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings

11 Identify the element described by the following. A. Group 7A(17), Period 4 1) Br2) Cl3) Mn B. Group 2A(2), Period 3 1) beryllium2) boron 3) magnesium C. Group 5A(15), Period 2 1) phosphorus 2) arsenic3) nitrogen Learning Check

12 A. Group 7A (17), Period 4 1) Br B. Group 2A (2), Period 3 3) magnesium C. Group 5A(15), Period 2 3) nitrogen Solution