1. Chapter 3 Atoms and Elements
3.7
Trends in Periodic Properties
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

2. 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.
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

3. 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
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

4. 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:
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

5. 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
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

6. Electron-Dot Symbol for Mg
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

7. Electron-Dot Symbols for Selected Elements
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

8. Learning Check
Write the electron-dot symbol for each of the following elements: Cl, C, N.
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

9. Solution
Write the electron-dot symbol for each of the following elements:
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

10. 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
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

11. Atomic Size
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

12. Atomic Size
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

13. 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
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

14. Ionization Energy
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

15. 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
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

16. Metallic Character
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

17. Summary of Trends in Periodic Table
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

18. 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?
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

19. Solution Given the following elements: C N Cl
Which is the largest atom? C
Which has the highest ionization energy? Cl
Which belongs to Group 5A? N
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.