1. Ionic and Covalent Bonding
Chapter 4 Section 2 Notes
Ionic and Covalent Bonding

2. What holds bonded atoms together?
Atoms bond when their valence electrons interact
Atoms with full outermost energy levels are less reactive (Noble Gases)
Atoms with partially filled energy levels are more reactive (Groups 1-17)
Goal of atoms: have a full outer energy level

3. What holds bonded atoms together?
Octet Rule: atoms tend to gain, lose, or share electrons so they have 8 electrons in their outer shell.
The positively charged nucleus attracts the negatively charged electrons; this bond holds 2 atoms together.
Bonds behave like flexible springs instead of like sticks

4. Electrons in Shells Electrons are placed in shells according to rules:
1st shell: can hold up to 2 electrons
2nd shell: can hold up to 8 electrons
3rd shell: can hold up to 18 electrons, but after 8, you move to the 4th shell

5. Na would like to: lose 1 electron
N would like to: gain 3 electrons
O would like to: gain 2 electrons

7. Electron Dot Diagrams H He:           
Symbols of atoms with dots to represent the valence-shell electrons
H He:
          
Li Be  B   C   N   O  : F  :Ne :
       
          
Na Mg  Al  Si  P S :Cl  :Ar :
       

8. Ionic Bonds
Ionic Bond: formed when metals react with nonmetals; electrons are transferred
Metals lose electrons to form POSITIVELY charged ions, or cations
Examples: Lithium, Sodium, Beryllium, Magnesium
Positive ions form when the number of electrons are less than the number of protons
Group 1 metals → ion+1
Group 2 metals → ion+2
Group 13 metals → ion+3

9. Ionic Bonding: One big greedy thief dog!!

10. Formation of Sodium Ion
Sodium atom Sodium ion
Na  – e  Na +
( = Ne)
11 p p+
11 e e-

11. Formation of Magnesium Ion
Magnesium atom Magnesium ion 
Mg  – 2e  Mg2+
(=Ne)
12 p p+
12 e e-

12. Some Typical Ions with Positive Charges (Cations)
Group 1 Group 2 Group 13
H+ Mg2+ Al3+
Li+ Ca2+
Na+ Sr2+
K+ Ba2+

13. Quick Quiz #1 A. Number of valence electrons in aluminum
1) 1 e ) 2 e- 3) 3 e-
B. Change in electrons for octet
1) lose 3e ) gain 3 e ) gain 5 e-
C. Ionic charge of aluminum
1) ) ) 3+

14. Quiz Quiz #1 Answers A. Number of valence electrons in aluminum
B. Change in electrons for octet
1) lose 3e-
C. Ionic charge of aluminum
3) 3+

15. Quick Quiz #2 Give the ionic charge for each of the following:
A. 12 p+ and 10 e-
1) 0 2) 2+ 3) 2-
B. 50p+ and 46 e-
1) 2+ 2) 4+ 3) 4-
C. 15 p+ and 18e-
2) ) 3- 3) 5-

16. Ionic Bonds
Nonmetals gain electrons to form NEGATIVELY charged ions, or anions
Examples: Oxygen, Sulfur, Fluorine, Chlorine
Negative ions form when the number of electrons is more than the number of protons
Group 15 nonmetals → ion-3
Group 16 nonmetals → ion-2
Group 17 nonmetals → ion-1

17. Ionic Bonds Electrons are transferred in ionic bonding
One atom gains electrons, and the other atoms loses electrons

18. Ionic Bonds
Example: Sodium loses one electron to get a +1 charge (Na+). Chlorine gains an electron to get a -1 charge (Cl-). Then, the oppositely charged ions attract each other and form a bond.

19. Ionic Bonds

20. Ionic Bonds
Ionic compounds are in the form of network structures; they therefore have high melting and boiling points because of the high amount of energy required to pull apart the bonds

21. Ionic Bonds Ratio of Ions
The chemical formula NaCl tells us there is 1 Na+ ion and 1 Cl- ion, forming a neutrally charged particle.
Since there is only one atom of each element, there is a 1:1 ratio
The chemical formula CaF2 tells us there is 1 Ca+2 ion and 2 F- ions. 2 F- ions are needed to balance out the +2 charge so the particle is neutral

22. Ionic Bonds Electricity:
Solid ionic compounds don’t conduct electricity
When dissolved in water, ionic compounds conduct electricity because the ions are free to move

23. Metallic Bonds
Metallic Bond: a bond formed by the attraction between positively charged metal ions and the electrons around them.
Occurs between atoms of metal elements

24. Metallic Bonds
The attraction between the nucleus and the neighboring atom’s electrons holds the atoms close together
Since the atoms are packed closely, the electrons move from atom to atom, which is why:
Metals conduct electricity
Metals are flexible and bend without breaking (ductile and malleable)

25. Covalent Bonds
Covalent Bond: a bond formed when atoms share one or more pair of electrons
Often made of molecules
Formed between nonmetal atoms
Atoms joined by covalent bonds share electrons

27. Covalent Bonds There are 2 types of covalent bonds:
Nonpolar covalent bonds: electrons are shared equally; often occurs between 2 atoms of the same element
Polar covalent bonds: electrons are shared unequally; often occurs between 2 atoms of different elements; shared electrons are attracted to the nucleus of 1 atom more than the other
Usually, electrons are more attracted to atoms of elements located to the right and closer to the top of the periodic table

28. Nonpolar Covalent Bond

29. Polar Covalent Bond
Note: Partial charges occur with polar covalent bonds

30. Structural Formulas When writing structural formulas:
1 line drawn indicates that atoms share 1 pair, or 2 electrons
Example: Cl-Cl
2 lines drawn indicate that atoms share 2 pair, or 4 electrons
Example: O=O
3 lines drawn indicate that 3 pair, or 6 electrons are being shared

31. Polyatomic Ions
A polyatomic ion is an ion made of 2 or more atoms that are covalently bonded and that act like a single ion
Some polyatomic anion names relate to their oxygen content
An anion ending in –ate is the ion with one more oxygen atom
An anion ending in –ite is the ion with one less oxygen atom
Examples: Sulfate (SO4-2) and Sulfite (SO3-2)