Physical Science
Chemistry REVIEW
Why do atoms Bond?

Brainstorm:

What is the Octet Rule?
Types of Bonds

Colvalent:

Ionic:
Writing Formulas

When writing a formula it is important to remember that every compound
has a charge of zero, unless stated otherwise



This means that the charge of the anions (negative) and cations
(positive) will add up to zero
Binary compounds are made of two monatomic ions

Monatomic ion are ions that contain only one type of element (i.e you
can find it on the periodic table)

Ex Na+, H+, O-2, N-3

Charges are found on the periodic table
Example of binary compounds

NaCl, CaCl, KF, Li2O
Polyatomic Compounds
 These compounds contain polyatomic ions
 A polyatomic ion is made up of more than one ion but it acts just like
monatomic ions do
 Charges and names of polyatomic ions can be found on the back of
your periodic tables
 **note** polyatomic ions are ALWAYS anions (negative)
 Examples: NO3-
CO3SO4-
Writing Formulas
 Find how many of each ion that you need to make the overall charge
equal zero
 Hint: use the charges to determine how many atoms you need

Na+1
C-4

Ca+2
C-4

Ca+1

K
 Na
(PO4)-3
O
(PO4)
Naming rules

Covalent naming:
•
•
•
Always write the least electronegative element first
The more electronegative element is then written, but to it the suffix –
ide is added to it
 Ex oxygen- oxide
 fluorine- fluoride
 nitrogen- nitride
We now find the problem of distinguishing between compounds with
more than one formula (ex CO, CO2)

You Try

NF3
To prevent this from occurring we add a greek prefix to the element
names

N2O4

OF2
Ionic Bonds
Rules
•
Separate the compound into cations and anions


•

Cations- the name will stay the same
Ex. Ca+2 stays as calcium

Anions- the suffix –ide is added to the element name
Ex. Br – becomes bromide Ion
To name the ionic compound add the names of the ions together


Ex. CaBr2
calcium + bromide = calcium bromide
Examples:
K O
2
 CaF2

BaO
Polyvalent metals
•
Some metals can have more than one charge therefore we have to
distinguish which charge the metal has


FeO- looking at the periodic table Fe could have a +2 or a +3 charge

Ex. FeO has one anion with a -2 charge, therefore the Fe must
balance that charge and have a +2 charge (the total anion and the
total cation charges must be equal)
To find it’s charge, look at the charge on the anion (and the number
of these charges)
•
Now that the charge on Fe is known as +2, we have to show that in it’s
name

We do this by adding a roman numeral to the cation

FeO- Fe has a +2 charge therefore the roman numeral II is added
after iron

FeO- iron (II) oxide
 Note only metals with more than one charge have to have the roman
numeral added to it
 Ex. Gallium (Ga) only has one charge; which is +3, therefore we don’t
have to add the roman numeral to it’s name
 Use the periodic table to determine which metals can have more
than one charge
 In pairs look at the periodic table and list those metals that can
have more than one charge
Balancing Equations
•
•
•
•
Write down the unbalanced equation
Draw boxes around each chemical formula- never ever change
anything inside the boxes
Make an element inventory- write down how many of each element you
have
Write numbers in front of the boxes to try to get the same number of
atoms on each side of the equation
Some of Mrs. Lalonde`s Helpful Hints for balancing equations
Save H for next to last, and O until last.
IF everything balances except for O, double all the coefficients and try
again.
(Shortcut) Polyatomic ions that appear on both sides of the equation
should be balanced as independent units

Zn + HCl ---> ZnCl2 + H2

KClO3 ---> KCl + O2

Zn + HCl ---> ZnCl2 + H2

S8 + F2 ---> SF6

Fe + O2 ---> Fe2O3

C2H6 + O2 ---> CO2 + H2O