Chapter 3 Atoms and Elements 3.7 Trends in Periodic Properties 1 Chemistry: An Introduction to...
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Transcript of Chapter 3 Atoms and Elements 3.7 Trends in Periodic Properties 1 Chemistry: An Introduction to...
Chapter 3
Atoms and Elements
3.7Trends in Periodic Properties
1
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.
Group Number and Valence Electrons
For representative elements in Groups 1A–8A, chemical properties are due to the number of valence electrons.
Valence electrons are the number of electrons in the outermost energy level.
The group number gives the number of valence electrons for the representative elements.
2
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.
Group Number and Valence Electrons
Group Number # Valence Electrons 1A 1 2A 2 3A 3 4A 4 5A 5 6A 6 7A 7 8A 8
3
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.
Electron-Dot Symbols
Electron-dot symbols
• are also known as Lewis structures
• represent the valence electrons as dots placed on sides of symbol
For example, Al = 2,8,3
Three valence electrons are represented as dots:
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Al
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.
Electron-Dot Symbol for Mg
Possible electron-dot symbols for magnesium, with the electron arrangement of 2,8,2,
• include 2 valence electrons, represented as dots
• can be drawn in more than one way
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Mg Mg
Mg Mg
Mg
Mg
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.
Electron-Dot Symbol for Mg6
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.
Electron-Dot Symbols for Selected Elements7
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.
Learning Check
Write the electron-dot symbol for each of the following elements: Cl, C, N.
8
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.
Solution
Write the electron-dot symbol for each of the following elements:
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C NCl
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.
Atomic Size
Atomic size• is determined by the atom’s atomic radius, the distance
between nucleus and outermost electrons
• increases for representative elements from top to bottom of the periodic table
• decreases within a period due to increased number of protons in nucleus
10
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.
Atomic Size11
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.
Atomic Size12
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.
Ionization Energy
Ionization energy
• is the energy required to remove one of the outermost electrons from an atom
Na(g) + energy (ionization) Na+(g) + e−
• decreases down a group, increases across a period from left to right
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Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.
Ionization Energy14
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.
Metallic Character
An element with metallic character is one that loses electrons easily.
Metallic character
• is more prevalent in metals on left side of periodic table
• is less for nonmetals on right side of periodic table that do not lose electrons easily
15
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.
Metallic Character16
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.
Summary of Trends in Periodic Table17
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.
Learning Check
Given the following elements: C N Cl
Which is the largest atom?
Which has the highest ionization energy?
Which belongs to Group 5A?
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Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.