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Chapter 3 Electronic Structure and the Periodic Law

3.1The Periodic Law and Table

Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings

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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.

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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.

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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.

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Groups and Periods

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Periodic Table by Meyer and Mendeleev

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Group Numbers

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.

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Names of Some Representative Elements

Several groups of representative elements are known by common names.

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Alkali Metals

Group 1A(1), the alkali metals, includes lithium, sodium, and potassium.

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Halogens

Group 7A(17) the halogens, includes chlorine, bromine, and iodine.

Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings

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Identify the element described by the following.

A. Group 7A(17), Period 4 1) Br 2) Cl 3) Mn

B. Group 2A(2), Period 3 1) beryllium 2) boron 3) magnesium

C. Group 5A(15), Period 2 1) phosphorus 2) arsenic 3) nitrogen

Learning Check

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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