1. Ions In general, atoms are electrically neutral
They have the same number of protons (+) as electrons (-)
However, because atoms can gain or lose electrons, they can become charged.

2. These atoms lose electrons These atoms gain electrons
IONS
An atom or a group of atoms that have gained or lost electrons
(it has a charge)
2 types
ANIONS
(negative ions)
CATIONS
(positive ions)
These atoms lose electrons
These atoms gain electrons
Ex. Na1+
Ex. Cl1-

3. TYPES OF BONDS Example 1. IONIC BONDS
– formed between oppositely charged ions (ex. between a metal and nonmetal)
-forms when electrons are transferred from one atom to another
Example
Na+1 combined with Cl-1
NaCl

4. Ionic Bonding NaCl 1st: Na gives up an electron to Cl
2nd: Forming Na+ & Cl-
3rd: Oppositely charged ions attract & form a “bond”
NaCl

5.
Sodium (Na) loses its one valence electron to Chlorine (Cl)
resulting in Na Cl
A negatively charged Cl ion
(-1)
A positively charged Na ion (+1) Na Cl

6. Ionic Bonding CaBr2 - Br Ca - Br
1st: Ca gives up an electron to each Br
Ionic Bonding
2nd: Forming Ca2+ & two Br-
3rd: Oppositely charged ions attract & form a “bond” Br - Ca 2+ Br -
CaBr2

7. Important!
When compounds formed by ionic bonds are dissolved in water, the solution will conduct electricity
Why?
Ions in solution are mobile & carry a charge, therefore can carry an electric current

8. TYPES OF BONDS 2. COVALENT BONDS Examples
-forms when electrons are shared between the atoms
-formed between two non-metals.
Examples
Cl2 H2 CO

9. 1st: Both Cl have a strong affinity for their valence electrons
Covalent Bonding
2nd: So both Cl atoms share a valence electron
3rd: Forming a “bond”

10. Cl2 is an example of covalent bonding.
Cl2 is an example of covalent bonding.
The chlorine atoms each share one of their valence electrons,
Their outermost shell is now full (it is stable)
H2 is another example of covalent bonding.
The hydrogen atoms each share their valence electron with one another.
Their outermost shell is now full (recall in the first shell there are only 2 valence electrons!)  

11. 1st: Both C & H have a strong affinity for their valence electrons
Covalent Bonding
2nd: So all atoms share their valence electron, forming a “covalent bond”

12. 1st: Both O & H have a strong affinity for their valence electrons
Covalent Bonding
2nd: So all atoms share their valence electron, forming a “covalent bond”

13. Important!
When compounds formed by covalent bonds are dissolved in water, the solution will NOT conduct electricity
Why?
There are no ions or free charges present, so no electricity can be conducted

14. Recall – ionic bonds are
Ex #1
Which of the following compounds have ionic bonds?
1. MgCl2
2. Al2O3
3. SO2
4. CH4
5. BeF2
6. SiO2
Recall – ionic bonds are
formed between a
metal & non-metal

15. Recall – covalent bonds
Ex #2
Which of the following compounds have covalent bonds?
1. C2H6
2. P2O5
3. NH3
4. Li2S
5. F2
6. AlCl3
Recall – covalent bonds
are formed between
non-metals or
metalloid & non-metal

16. Ex #3
Which of the following compounds when dissolved in water will produce an electrolytic solution?
1. C6H12O6
2. H2S
3. C2H4OH
4. MgCl2
5. AlBr3
Recall – ionic compounds
when dissolved in water
will conduct electricity

17. Ex #4
Which of the following compounds when dissolved in water will NOT form ions?
1. Fe2O3
2. H2
3. Ca(OH)2
4. MgS
5. NO2
Recall – only ionic
compounds when
dissolved in water
will form ions

18. Same as ions except they are in groups instead of single atoms
POLYATOMIC IONS
A group of elements bonded together to form a single ion with their own charge
Same as ions except they are in groups instead of single atoms

19. POLYATOMIC IONS Ex. OH_ (hydroxide ion) It has a charge of 1-
Consists of an oxygen atom and a hydrogen atom
Treated like one single ion even though it is made up of 2 atoms

20. POLYATOMIC IONS Ex. SO42- (sulfate ion) It has a charge of 2-
Consists of a sulfur atom and four oxygen atoms

21. Other polyatomic ions... Charge on ion

22. You must memorize the following names and charges for these polyatomic ions:
OH-1 Hydroxide
NH4+1 Ammonium
SO4-2 Sulfate
CO3-2 Carbonate
PO4-3 Phosphate
NO3-1 Nitrate

23. How do we write formulas using polyatomic ions???
MOLECULAR FORMULAS
How do we write formulas using polyatomic ions???
Ex.
Na1+
SO42-
Sodium sulfate
Na2SO4
Treat the polyatomic ion as a single item & note the charge (sulfate has a charge of 2-)
2. Note the charge on the other element (sodium (Na) has a charge of 1+)
3. Use the crossover rule to find the formula (Na2SO4)

24. MOLECULAR FORMULAS Ex. Magnesium Hydroxide Mg2+ OH1- Mg(OH)2
Treat the polyatomic ion as a single item & note the charge
2. Note the charge on the other element
3. Use the crossover rule to find the formula

25. MOLECULAR FORMULAS Ex. Lithium Phosphate Li+ PO43- Li3PO4
Treat the polyatomic ion as a single item & note the charge
2. Note the charge on the other element
3. Use the crossover rule to find the formula

26. MOLECULAR FORMULAS Ex. Calcium Carbonate Ca2+ CO32- CaCO3 Ca2(CO3)2
Treat the polyatomic ion as a single item & note the charge
2. Note the charge on the other element
3. Use the crossover rule to find the formula

27. MOLECULAR FORMULAS Ex. Ammonium bromide NH4+ Br- NH4Br
Treat the polyatomic ion as a single item & note the charge
2. Note the charge on the other element
3. Use the crossover rule to find the formula

28. PRACTICE PROBLEMS
Worksheet # 1
Study guide, Module 3, page 8 and 9