1. The Outer Electrons, Ions & Chemical Bonding1

2. Ch. 5 - Atoms, Ions & Chemical Bonds
I. Why Atoms Combine (p )
Chemical Formula
Chemical Bond
Stability

3. B. Chemical Bond
Strong attractive force between atoms or ions in a molecule or compound.
Formed by:
transferring e- (losing or gaining)
sharing e-

4. Outer Shells Electrons (valance electrons)
Most atoms form bonds using only their outside electrons, these are known as valance electrons; the electrons in an atom’s outermost energy level. 4

5. Outer Shells Electrons (valance electrons) continued………
Valence Electrons and the Periodic Table
Remember…… You can use the periodic table to determine the number of valence electrons in some elements 5

6. When using a table with groups 3A to 8A Listed, the group # equals the number of Valence electrons
(These are Groups 3A-8A) 1A 2A 3A 4A 5A 6A 7A
(Groups 3B-12B) 6

7. Ions……..
An atom is neutral because the number of (-) electrons in an atom equals the number of (+) protons.
The (+) and (-) charges cancel each other out.
But when an atom gains or loses electrons, it becomes a charged particle called an ion. 7

8. Forming Positive Ions
Atoms of most metals have few valence (outside) electrons
They tend to lose these valence electrons and form positive ions
This leaves 8 electrons in the remaining outside shell 8

9. Forming Negative Ions
The outer energy level of nonmetal atoms is almost full.
Nonmetal atoms tend to gain electrons and become negative ions
This brings their outside shell to 8 electrons 9

10. Why would atoms want to swap or share electrons?
It’s all about atoms wanting a full outside or valence shell (they want 8 e-)
Remember, the number of electrons in an atoms outside shell or valence level can be determined from the periodic table group number
It is the number of electrons in the outermost level that determine how an atom will bond 10

11. Ne C. Stability Octet Rule (The Rule of Eight)
most atoms form bonds in order to have 8 valence e-
full outer energy level
like the Noble Gases! Ne
Stability is the driving force behind bond formation!

12. C. Stability
Transferring e-
Sharing e-

13. To Bond or Not to Bond
Filling the Outermost Level An atom that has fewer than 8 valence electrons wants to form bonds by gaining or losing electrons
Atoms bond by gaining or losing electrons (ionic) or sharing electrons (covalent) to fill the outermost energy level 13

14. To Bond or not to Bond
The number of electrons in the outermost energy level of an atom determine whether an atom will form bonds.
Atoms that have 8 electrons in their outermost energy level do not usually form bonds. The outermost energy level is considered to be full if it contains 8 electrons
These are the noble gases (Group 8A or 18) 14

15. 15

16. Today’s Lesson…… Ions & Ionic Compounds16

17. Ions make molecules & compounds…..
Remember…….
When an atom gains or loses electrons, it becomes a charged particle called an ion
Whether electrons are lost or gained depends on the number of valence electrons
When ions are formed by transferring electrons from one atom to another atom an ionic bond is formed
When this happens a molecule is formed 17

18. Ions
Atoms where the number of ELECTRONS are different than the number of protons
1e-
Sodium
Cl -1
8e-
Na +1
2e-
Anion
8e-
7e-
11 p+
8e-
12 N
2e-
This is a shorter version of the same lesson. Use this if you intend to do a basic introduction or would like to spend the other half of class doing an isotope/ions worksheet.
This slide is on “Hide” mode. To allow it to show, right-click it to and select “Hide Slide”.
17 p+
18 N
Cation
Chlorine 18 18

19. A positively charged ion
Cation…… pronounced
“cat” “i on ”:
A positively charged ion
Anion…… pronounced “Ann” – “i on ”:
A negatively charged ion 19

20. Name: ________________
Period : ______
Ions
Atoms where the number of ELECTRONS are different than the number of protons
S -2
Mg +2
This is a shorter version of the same lesson. Use this if you intend to do a basic introduction or would like to spend the other half of class doing an isotope/ions worksheet.
This slide is on “Hide” mode. To allow it to show, right-click it to and select “Hide Slide”. 20 20

21. Name: ________________
Period : ______
Ions
Atoms where the number of ELECTRONS are different than the number of protons
O -2
Be +2
This is a shorter version of the same lesson. Use this if you intend to do a basic introduction or would like to spend the other half of class doing an isotope/ions worksheet.
This slide is on “Hide” mode. To allow it to show, right-click it to and select “Hide Slide”. 21 21

22. Ionic Compounds
When ionic bonds form, the number of electrons lost by the metal atoms equals the number gained by the nonmetal atoms.
The ions that bond are charged, but the compound formed is neutral because the charges of the ions cancel each other. 22

23. Ionic Compounds, continued
When ions bond, they form a repeating three-dimensional pattern called a crystal lattice, such as the one shown below.
Properties of ionic compounds include brittleness, high melting points, and high boiling points.
Cl-1
Na+1 23

24. Ionic Compounds, continued
Ionic Compounds, continued
NaCl
 Sodium chloride
AlBr3
 Aluminum bromide
Ca3P2
 Calcium phosphide
SrI2
 Strontium iodide
FeCl2
 Iron(II) chloride or ferrous chloride      The cation charge must be specified       since iron can form more than one charge.
CuSO4
Cu2+ S042- 24

25. H2O A. Chemical Formula Shows: 1) elements in the compound
2) ratio of their atoms
H2O
1 oxygen atom
2 hydrogen atoms

26. 26

27. The number of valance electrons determines the typical charge on the ions that atoms form27

28. What you should have learned so far…….
Why ionic bonds form
What a cation and anion are
What charge will be on the ions in an ionic bond
How to determine the molecular formula from the type of ions that form
You can do it! 28

29. Periodic Table: electron behavior
The periodic table can be classified by the behavior of their electrons

30. 3. Trend in Ionization Potential
The energy required to remove the valence electron from an atomic specie. Largest toward NE corner of PT since these atoms hold on to their valence e- the tightest.