1. Ionic Compounds

2. Chemistry Joke
Q: Why do chemists like nitrates so much?
A: They’re cheaper than day rates!

3. A Review
Ion: atom or group of atoms that have a positive or negative charge
Ions form when an atom or group of atoms gains or loses electrons
METALS lose electrons to form positive CATIONS.
NONMETALS gain electrons to form negative ANIONS

4. Monatomic Ions Ions consisting of only 1 atom
Having One Atom!
Monatomic Ions
Ions consisting of only 1 atom
The charge for ions formed from representative elements can be determined by looking at the periodic table
Group 1A metals form cations with a 1+ charge
Group 2A metals form cations with a 2+ charge
Group 3A metals form cations with a 3+ charge
Group 5A nonmetals form anions with a 3- charge
Group 6A nonmetals form anions with a 2- charge
Group 7A nonmetals form anions with a 1- charge
Group 8A elements do not form ions

5. Having Many Atoms!
Polyatomic Ions
Tightly bound groups of atoms that behave as a unit and carry a charge
Ex: The 10 you had to memorize.
1- charge:
2- charge:
3- charge:
1+ charge:
NO3- NO OH- ClO C2H3O2-
CO SO SO32-
PO43-
NH4+

6. Naming Monatomic Cations
The name of a cation is the SAME as the name of the element!!
Ex: Na atom forms a sodium cation
Ex: Li atom forms a lithium cation
How would you name the following ion:
Al+3
Aluminum ion

7. Naming Monatomic Anions
The name of a MONAtomic ion ends in “ide”
Ex: Chlorine atom gains 1 electron to become the CHLORIDE anion
Ex: Oxygen gains 2 electrons to become an anion named OXIDE
What would we name the following ion?
S-2
Sulfide ion

8. Practice: What do we call: A strontium atom when it loses 2 electrons
An iodine atom when it gains 1 electron
A phosphorus atom when it gains 3 electrons?
Strontium ion
Iodide ion
Phosphide ion

9. Naming Ionic Compounds
The cation comes 1st and keeps its name.
Monatomic anions end in “ide”
Polyatomic cations and anions keep their names.
LiCl
K2SO4
Lithium Chloride
MgF2
Potassium Sulfate
Magnesium Fluoride
LiNO3
MgCO3
Lithium Nitrate
Be(OH)2
Magnesium Carbonate
Beryllium Hydroxide
NH4Cl
Ammonium Chloride

10. Writing the Formulas!
Cations and anions combine in a whole number ratio that produces a neutral compound.
The total positive charge of the cations will equal the total negative charge of the anions.
For example: 1 Al+3 combines with 3 F-1
(1 x +3) cancels with (3 x -1)

11. 3 Step Process for Writing Ionic Formulas
Criss Cross Method
3 Step Process for Writing Ionic Formulas
Write the ions with their charges
The charges are known from the periodic table or memorized for polyatomic ions.
Cross the charge numbers (dropping the + or -) to form the subscripts. (Subscripts of 1 are not written.)
Simplify the subscripts to the lowest whole number ratio

12. Writing Formulas for Ionic Compounds
Write the formula for magnesium chloride.
Write the ions with their charges
The charges are known from the periodic table.
Cross the charge numbers (dropping the + or -) to form the subscripts. (Subscripts of 1 are not written.)
Simplify the subscripts to the lowest whole number ratio
Magnesium is in Group 2A and forms a 2+ charge.
Chlorine is in Group 7A and forms a 1- charge.
Mg2+
Cl1- Mg Cl
MgCl2

13. Writing Formulas for Ionic Compounds
Write the formula for beryllium oxide.
Write the ions with their charges
The charges are known from the periodic table.
Cross the charge numbers (dropping the + or -) to form the subscripts
Simplify the subscripts to the lowest whole number ratio. (If both subscripts are the same, they can be dropped.)
Beryllium is in Group 2A and forms a 2+ charge.
Oxygen is in Group 6A and forms a 2- charge.
Be2+
O2- Be O
Be2O2
BeO

14. Writing Formulas for Ionic Compounds
With Polyatomic Ions
Follow the same 3 steps.
Just add parentheses around the polyatomic ion before it gets a subscript

15. Writing Formulas for Polyatomic Ionic Compounds
Write the formula for calcium hydroxide.
Write the ions with their charges
Cross the charge numbers
(dropping the + or -) to form the subscripts
Subscripts of 1 are not written
Simplify the subscripts
Remember to add parentheses around the polyatomic ion if a subscript has been added!
Calcium is in Group 2A and forms a 2+ charge.
Hydroxide is a polyatomic ion that has a 1- charge.
Ca2+
OH1- Ca OH
There are 2 Hydroxide ions not just 2 Hydrogen atoms.
CaOH2
Ca(OH)2

16. Try Some Na2CO3 KOH Mg3(PO4)2 Sodium Carbonate Potassium Hydroxide
Magnesium Phosphate
KOH
Mg3(PO4)2

17. Chemistry Joke
Q: What happened when someone told a joke to two helium atoms?
A:They went, “He He!!”