Two types of chemical compounds: Ionic and Molecular
IONIC compounds
are formed as the ____________________________________ completely making them a charged ion, this is
known as an ____________________.
are formed due to ______________________________ between the positive ____________ and the negative
___________. Therefore, ionic compounds contain ______________________
dissolve in water forming solutions that conduct electricity. These solutions have electrolytes as the ions are
free to move around the solution.
MOLECULAR compounds
contain Atoms or Groups of Atoms that are not charged
combination of atoms make up a molecule
they join together by ___________________________, this is known as a _________________
molecular compounds contain ____________________________
5.8 Notes
Rules for Writing Formulas
The cation (metal) symbol is written first. The anion (non-metal) symbol is written last.
Write the charge on the top of the appropriate symbol. Check your periodic table to get charges
“Cross” the charges by placing the charge of the first ion (number only, not the + or −sign) as a
subscript for the second ion, and the charge of the second ion as a subscript for the first ion. “Ones”
can be omitted.
If a polyatomic ion is present, the subscript must be placed outside the brackets.
Reduce the numbers, if possible, to the lowest whole number ratio by dividing by the LCM.
a) Li+ and S2- { Li2S }
d) Mg2+ and N3-
{ Mg3N2 }
b) Sn4+ and O2- { SnO2 }
e) Al3+ and (SO4)2¯
{ Al2(SO4)3 }
c) H+ and Cl- { HCl }
f) NH4+ and S2¯
{ (NH4)2 S }
You should be able to complete #’s 1, 2, 3, 5, 7, and 9 on page 195
Nomenclature (Naming) of Ionic Compounds
All ionic compounds that you will be naming are composed of ONLY 2 ions. To name a compound divide the
compound into the cation (first element in formula) and anion (last 1 or more elements) and give each ion its
proper name.
cation(+)
anion(¯ )
Compound
Mg 2+ Cl ¯
MgCl2
magnesium chloride
magnesium chloride
Fe3+ OH ¯
Fe(OH)3
iron (III) hydroxide
iron (III)hydroxide
Ba2+ PO43¯
Ba3(PO4)2
barium phosphate
barium phosphate
**NH4+ HCO3¯
NH4 (HCO3)
ammonium bicarbonate
ammonium bicarbonate
**only case where the cation contains more than one element
** remember that you only change the anion to “ide” – do not change the name of the metal
You should be able to complete #’s 4, 6, 8 on page 195
Section 5.9
Polyatomic ions are tightly bound groups of atoms that behave as a unit and carry a charge.
OH¯ hydroxide
O and H act together as a unit
overall charge is 1¯
SO32¯ sulfite ion
1 sulfur, and 3 oxygen acting together
overall charge is 2¯
Do not confuse polyatomic ions with molecules, which are a group of atoms behaving as a unit but not
carrying a charge.
Polyatomic ions usually have an ate or ite ending on their name. This reflects the number of O atoms in
the ion. The ion with the ate ending has more oxygen than the ion with the ite ending. If polyatomic
ions do not contain O they end in ide.
Polyatomic ions are usually anions; the only polyatomic cation that you need to know is NH4+
(ammonium).
** There is a chart of polyatomic ions on the back of your periodic table to help you! 
Oxyacids – special polyatomic compounds that occur when hydrogen combines with polyatomic ions
containing _____________________________.
Writing formulas for polyatomic compounds
______________ : Write the symbol of the cation and then the polyatomic group
______________ : Write ionic charges
______________: Choose the # of ions to balance the charge
______________: Write the formula using subscripts
Note: you may need to place brackets around a polyatomic ion symbol if its numerical subscript is greater
than one.
Please complete #’s 1-4 on page 198
Section 5.11 Notes
E.g. Cl2 (g) – Cl atoms are held together with covalent bond
__________________________ – Compounds consisting of neutral molecules. Formed when nonmetal atoms
share electrons to form stable arrangements
Rules for Naming Molecular Compounds
1.
Write the name of the most metallic atom first (it will be furthest left on periodic table). Do not use
an ide ending.
2.
Write the name of the second element with an ide ending.
3.
Add a Greek prefix to each name indicating how many atoms are bonded.
4.
Exceptions: Do not add the prefix MONO to the first name. Drop the ‘a’ or ‘o’ from the prefix if the
first letter of the element is the same.
Greek Prefix
1
mono
2
di
3
tri
4
tetra
5
penta
6
hexa
7
hepta
8
octa
9
nona
10
deca
Examples:
CO is called carbon monoxide
CS2 is called Carbon disulfide
CH4 is carbon tetrahydride
Formulae of molecular compounds
Do not reduce the subscript numbers to the lowest whole number.
Charges are not used to determine the formula of molecules. We do NOT drop and switch!
Remember the diatomics and the polyatomics:
I
I2
Have No
H2
N2
Bright
Br2
Or
O2
Clever
Cl2
Friends
F2
P4 and S8
Draw the Lewis structures for each atom,
draw
1. draw circles to show the electrons that are shared, and then write the bond structure and chemical
formula
See figure 3 and figure 5 on page 202
Complete #’s 1- 7 on page 204