1. Section 1 – pg 176 Atoms, Bonding, and the Periodic Table
Chapter 5
Section 1 – pg 176
Atoms, Bonding, and the Periodic Table

2. Valence Electrons and Bonding
Pg 176
Valence Electrons and Bonding
Valence Electrons: electrons that have the highest energy level and are held most loosely
The number of valence electrons in an atom of an element determines many properties of that element, including the ways in which the atom can bond with other atoms

3. Electron Dot Diagram Pg 177
Each element has a specific number of valence electrons, ranging from 1-8
Electron Dot Diagram: includes the symbol for the element surrounded by dots
Each dot stands for one valence electron

4. Chemical Bonds and Stability
Pg 177
Chemical Bonds and Stability
Atoms of most elements are more stable (less reactive) when they have 8 valence electrons
This is why atoms of neon, argon, krypton and xenon are very unreactive – they each have 8 valence electrons
These atoms do not easily form compounds
Some small atoms (such as helium) are stable with just two valence electrons

5. Atoms usually react to become more stable
Pg 177
Atoms usually react to become more stable
They will either gain electrons until they have 8
They will give up loosely held valence electrons
When an atom either gains or looses electrons, they can become chemically bonded (combined) with the other atom
Chemical Bond: the force of attraction that holds two atoms together as a result of the rearranging of electrons between them

6. How the Periodic Table Works
Pg 178
How the Periodic Table Works
The periodic table reveals the underlying atomic structure of atoms, including the arrangement of the electrons

7. Relating Periods and Groups
Pg 178
Relating Periods and Groups
As the atomic # increases, so does the number of electrons
A given period ends when the # of valence electrons reaches 8
Elements within a group (column) always have the same # of valence electrons and therefore, similar properties

8. Pg 179
Inert Gases
Group 18 elements have 8 valence electrons (except for Helium which has 2)
These elements are stable and therefore unlikely to transfer electrons or react easily with other elements

9. Reactive Nonmetals and Metals
Pg 179
Reactive Nonmetals and Metals
Group 17 (Halogens) have 1 valence electrons -> gaining 1 electron would make them stable
They react easily with other elements whose atoms can give up or share electrons
Group 1 (Alkali Metal) have only one valence electron
Can easily become stable by losing their one valence electron -> very reactive

10. Other Metals Pg 180 Groups 2 – 12 (metals) have 1-3 valence electrons
React by losing these valence electrons, esp. when combined with oxygen or a halogen
Reactivity of metals decreases from left to right
In Groups 1 & 2, reactivity increases from top to bottom

11. Pg 181
Other Nonmetals
All of the nonmetals have four or more valence electrons and become stable when they have a set of 8
Combine with metals by gaining electrons
Combine with other nonmetals by sharing electrons

12. Semimetals Pg 182 Have 3-6 valence electrons
Can either lose or share electrons when combined with other elements

13. Pg 182
Hydrogen
Has 1 valence electron
NOT a metal

14. Chapter 5 Section 1 Homework – pg 182

15. 1A. What are valence electrons?

16. 1B. What role do valence electrons play in the formation of compounds from elements?

17. 1C. Do oxygen atoms become more stable or less stable when oxygen forms compounds? Explain

18. 2A. Summarize how the periodic table is organized, and tell why this organization is useful.

19. 2B. Why do the properties of elements change in a regular way across a period?

20. 2C. Explain the reactivity of the inert gases in terms of valence electrons.