1. Chemistry - Shearer - Standard 1
Valence Electrons
Standard 1d
Students know how to use the periodic table to determine the number of electrons available for bonding.
Chemistry - Shearer - Standard 1

2. Why are Valence Electrons Important?

3. Review… Protons and Neutrons are in the nucleus
Electrons are located in energy levels (shells) that surround the nucleus
Electrons in the outer shell of an atom are responsible for chemical bonds!
If an outer shell holds 8 valence electrons – no bonding will take place!

4. How many electrons are available for bonding?
Valence Electrons
Electrons are arranged around the nucleus in 7 specific areas called energy levels.
The valence electrons participate in the formation of chemical bonds.
Valence electrons are the outermost electrons.
How many electrons are available for bonding?
Chemistry - Shearer - Standard 1

5. 1 2 3 4 E7 5 6 E6 E5 7 E4 E3 E2 E1
nucleus

6. How to Determine Valence Electrons
You can determine how many valence electrons an element has by determining which group it is in. 1 8 2 3 4 5 6 7 2

7. Octet Rule
Elements with 8 valence electrons have a full outer shell and will not bond! (Noble Gases)
8 outer electrons is the ideal number of valence electrons that all atoms seem to want.
All elements want to be stable like the noble gases (have 8 electrons in their outer shells).

8. Valence Electrons and Bonding
The only electrons available for bonding with other atoms are the outermost electrons.
Only These
Chemistry - Shearer - Standard 1

9. Chemistry - Shearer - Standard 1
The number of outer or valence electrons can be determined by their location on the periodic table.
Chemistry - Shearer - Standard 1

10. Noble Gases and Bonding
(Group 18 or 8A) = 8 valence electrons
Do not react with other atoms (inert).
Chemistry - Shearer - Standard 1

11. The Snobs of the Periodic Table
“We don’t want to bond with anyone!”
Chemistry - Shearer - Standard 1

12. How is helium a noble gas without 8 valence electrons?
What about Helium?
Helium only has 2 electrons.
How is helium a noble gas without 8 valence electrons?
Helium only has 1 energy level.
The 1st energy level can only hold 2 electrons!
Thus, helium has a full outer shell.

13. Alkali Metals and Bonding
One valence electron available for bonding.
These metals readily give this electron to another atom to form an ionic bond.
Chemistry - Shearer - Standard 1

14. “Please take my electron! I really want to look like a Noble Gas!”
Chemistry - Shearer - Standard 1

15. Alkaline Earth Metals and Bonding
Two valence electrons for bonding.
Gives 2 electrons away to form ionic bonds.
How many electrons in the second to last shell?

16. Chemistry - Shearer - Standard 1
“My two electrons need to go, because my second to last shell is full!”
2 e-
Chemistry - Shearer - Standard 1

17. Transition Metals and Bonding
Most have 2 valence electrons.
These metals often give these electrons to another atom to form an ionic bond.
Utilize another
process to find the
ve-

18. Chemistry - Shearer - Standard 1
“Some transition elements are found free in nature while others give 2 electrons!”
2e-
Chemistry - Shearer - Standard 1

19. The Halogens and Bonding
Group 17 or 7A = seven valence electrons.
These nonmetals often take one electron from another atom to form an ionic bond.

20. Chemistry - Shearer - Standard 1
“Gaining one electron will make my valence 8! So you better watch out cause your electron I will take!”
7 e-
Again Group 18 or 8A elements each have eight valence electrons.
These noble gases have the correct number of electrons and generally will not form chemical bonds.
Chemistry - Shearer - Standard 1

21. Lewis Dots Also known as electron dot diagrams
Useful tool for determining how an element will bond
Includes the element symbol and a group of 1-8 dots which shows the configuration of the outer-most electron shell of the atom, also called the valence shell.

22. Lewis Dot Examples